79  The Manifestation of Teacher Leadership in Vietnamese National Educational

competence, Vietnam ABSTRACT The critical importance of teacher leadership roles in students’ academic achievements and school improvement is widely recognized. Preparing teachers for taking leadership roles, therefore, is requisite, particularly in response to the dynamic and changing nature of the present-day teaching profession. However, there is a lack of research into how teachers are provided with skills and knowledge to serve the leadership role, both formally and informally. The study employed The Teacher Leader Model Standards (TLMS) developed by the Teacher Leadership Exploratory Consortium (2011) to explore the manifestation of teacher leadership knowledge and competencies in policies on the teaching profession in the Vietnamese context. The analysis of 61 in-effect national policy documents on teaching profession standards and teacher professional development programs reveals that these policy documents have presented a broad but incomplete view of teacher leadership. Percentage-wise, teacher leadership is far from a salient manifestation within policy documents, indicating that it has not yet been considered a core competence in the teaching profession at the national policy level. In addition, there are crucial aspects of teacher leadership that have been neglected, while a lack of differentiation between teacher and principal leadership still remains in the documents. Based on the findings, the study proposes recommendations to the teachers, school leaders and policy makers on the development of


INTRODUCTION
Teacher leadership plays a critical role in improving education quality by influencing their colleagues' professional development and their students' academic achievements. There is evidence of the positive relationship between teacher leadership and the improvement of teaching quality and school standards (David et al., 2000;Hallinger & Heck, 2011;Harris & Muijs, 2005;Lai & Cheung, 2015). Much research has been done to show ample evidence of the positive effect of teacher leadership on other teachers' self-efficacy and self-esteem (Angelle & Teague, 2014;Friedman, 2011) as well as their improved instructional practices (Supovitz et al., 2010). This, in turn, leads to improved student performance (i.e. academic performance and engagement) (Poekert et al., 2016;Supovitz et al., 2010;Yost et al., 2009). Collectively, teacher leadership contributes to not only the development of a positive culture in their own school (Beachum & Dentith, 2004) but also extends its impact on professional learning

LITERATURE REVIEW
Previous studies focusing on teacher leadership have examined the development of teacher leadership and its relationship with students' academic achievements and school development (Ado, 2016;King et al., 2019;Lowery-Moore et al., 2016;Oplatka & Tako, 2009;Uribe-Flórez et al., 2014). The important roles and contributions of teachers (including early career teachers) to leadership in schools have compellingly drawn our attention to the research on the stages and approaches of leadership development for teachers. Firstly, the literature maintains that leadership development is an ongoing process that should start from the early stages of pre-service teacher education (e.g., Bond, 2011;Quinn et al., 2006). Research has evidenced multiple leadership roles and their enactment by teachers across different stages of their professional careers (Allen, 2016;Muijs et al., 2013). Examples of teacher leadership roles include coordination and management (Avidov-Ungaar & Shamir-Inbal, 2017), professional development of colleagues (Allen, 2016), leading and participating in curricular change and reform (Baecher, 2012;Firestone & Martinez, 2007), parental and community involvement (Frost, 2012), and action research (Margolis, 2008). These studies revealed that teachers could serve different leadership roles across the many responsibilities a teacher has, such as a curriculum design.
A noteworthy finding that emerged from international literature is the positive effects of teacher leadership on student learning (Sebastian et al., 2016;Supovitz et al., 2010). These studies show that when teachers serve leadership roles, the schools' collaborative culture can be seen in the harmony that is created among teachers, students, and parents. However, the latest review of international research on teacher leadership has highlighted that teachers experience stressors and challenges when they take the lead role in a teaching and learning position as a result of inadequate preparation for leadership enactment . This indicates that teachers should be provided with leadership knowledge and competencies through a single course or subject on leadership and management (Turnbull, 2005). Other forms of leadership education include integrating elements of leadership and management across courses in a teacher education program (Xu & Patmor, 2012) and developing pre-service teachers' leadership competencies through service-learning (Ado, 2016;Bond & Sterrett, 2014). The questions around which models and approaches best support pre-service teachers with leadership competencies are yet to be clarified; how leadership knowledge and competencies can be a component in teacher education programs depends much on the policies which stipulate regulations on this.

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 81  In Vietnam, research into leadership within the school context is scarce and limited to formal leadership positions such as school principals or vice-principals. For example,  discover that teachers are reluctant to take on leadership roles at schools. According to this study, while school leaders perceive the importance of teachers' participation in decision-making in terms of increasing their responsibility to the school and expanding grassroots democracy, teachers are not active enough to contribute to this process. The popular decision-making process of the schools that were involved in their study as a result of Confucian cultural values, in which decision making is mainly based on age and hierarchical status. Another study by  investigating how school principals enact their leadership roles in the Vietnamese context reveals that two leadership styles were applied at three schools participating in the study, including authoritarian and moral leadership styles. The autocratic leadership shows the power that the leaders use to influence staff and teachers and to impose their viewpoints over them. Whereas gaining staff's trust, respect, and commitment by setting standards and norms of behavior is demonstrated in moral authority. The findings showed the enactment of school leadership is strongly influenced by "goals of education as well as the sociocultural and political-institutional values and norms of the society" (p. 558), and leadership styles can impact teachers' engagement, commitment, and contribution to school improvement.
The review revealed that teachers could take different leadership roles in according to the responsibilities they take in their teaching careers, such as being a subject teacher or a homeroom teacher. However, in the Vietnamese context, teacher leadership, as shown in the reviewed studies, were limited to formal leadership positions. As policies on teaching positions regulate teacher leadership development and enactment, gaining an understanding of how teacher leadership is perceived by policy makers manifested in relevant policy documents in the Vietnamese context is critically important.

Analytical Framework
There has been a diverse range of definitions concerning teacher leadership , resulting in different models describing the development and constituents of this construct (Wenner & Campbell, 2018) as well as the impact that teacher leaders can bring in (Nolan & Palazzolo, 2011). These scattered efforts lead to a lack of a common vocabulary in the field to produce guidance for relevant policies and practices (Berg et al., 2014). This gap has recently been filled by the Teacher Leader Model Standards (TLMS), which establish a set of professional standards designed to "codify, promote, and support teacher leadership" (Teacher Leadership Exploratory Consortium, 2011, p. 8). Aiming to encourage dialogue among stakeholders about the competencies required of teacher leaders (Teacher Leadership Exploratory Consortium, 2011), the TLMS provides a helpful framework for discussing teacher leadership (Ado, 2016) toward establishing a consensus about how teacher leaders might contribute to school improvement (Berg et al., 2014;Kajitani, 2015).
Based on a thorough review of research and related literature, existing teacher education programs and practices, and numerous interviews with teacher leaders (Berg et al., 2014), the TLMS has further developed the work of York- Barr and Duke (2004, p. 287-288) who define teacher leadership as "the process by which teachers, individually or collectively, influence their colleagues, principals, and other members of the school community to improve teaching and learning practices with the aim of increased student learning and achievement". Specifically, the TLMS has built upon the previous literature (Barth, 1990;Danielson, 2006;Darling-Hammond et al., 1995;Greenlee, 2007) by steering away from the top down model in highlighting the critical contributions of teachers to the success of the school and student learning via their collaboration, development of professional learning communities, sharing of best practices, and reflective practice (Cosenza, 2015).
Consisting of seven domains, with each domain containing various dimensions in the forms of teacher functions that describe the knowledge and skills required of a teacher leader, the Standards outline a broad range of terrains of teacher leadership, presenting multiple ways teachers leaders can act and contribute to school improvement (Ado, 2016) by providing a set of functions or sample actions to depict a range of leadership behaviors in each domain (Berg et al., 2014). In this regard, the TLMS clearly articulate the possible roles and responsibilities teacher leaders take (Ado, 2016) in a deep, specific and comprehensive framework (Hunzicker, 2017) in comparison to earlier definitions of teacher leadership (Danielson, 2007;Muijs et al., 2013) which tend to be too abstract (Ado, 2016) to be incorporated in relevant policies or teacher leadership development programs.
Primarily designed to guide teacher leader preparation programs, policy and practice (Berg et al., 2014;Teacher Leader Model Standards, 2011), the TLMS was welcomed by both educators and policy makers soon after its release,

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 82  indicating an urgent need for such a framework (Berg et al., 2014;Mangin, 2016). The American Association of Colleges for Teacher Education (2011) acknowledged that the TLMS is of 'great importance and relevance to educators and prepares future educators (Dagen et al., 2017). Researchers also quickly examine the reliability and usefulness of the Standards using both quantitative (Mosley, 2012;Shelton, 2014) and qualitative measures (Ado, 2016;Berg et al., 2014;Gallucci, 2012;Lotter et al., 2020).
Nevertheless, the Standards are not immune from critiques. Berg et al. (2014), in their content analysis of the TLMS within the content of four existing, well-known teacher leader preparation programs, criticise the Standards for neglect of the importance of teachers' ability to develop a shared vision for improvement of their schools (Dagen et al., 2017). Another issue confirmed by Lotter et al. (2020) in their study about a rural teacher leadership development program is a lack of focus on content-specific knowledge and/or instructional expertise. However, as these two studies focus primarily on teacher leader preparation programs, we assume that the above issues of the TLMS are only relevant in such contexts.
Accordingly, we chose the TLMS to be the analytical framework for this study because, firstly, the Standards have been recognized and validated in both theory and practice, thereby increasing the reliability of the findings (Dey, 2003). Secondly, the Standards are more advanced compared with other frameworks and/or models in terms of providing detailed descriptions of possible functions of teacher leaders (Ado, 2016), making it more applicable for the content analysis method of this study. We, therefore, employ the TLMS as an analytical framework upon which the perceptions of Vietnamese policy makers regarding teacher leadership will be explored. By comparing the findings with what is described in the TLMS, we expect to identify the gaps between TLMS and the viewpoints of Vietnamese policy makers, thereby helping us a better understanding of how teacher leadership is defined and/or perceived in the context of Vietnamese educational policies.
We understand and acknowledge that contextual variations inevitably exist, especially when the TLMS were developed based on the American context, which is very different from that of Vietnam, where the topic of teacher leadership is still in its infancy. However, as the Teacher Leadership Exploratory Consortium (2011) noted that the Standards were developed to facilitate dialogue among stakeholders, instead of seeking to provide a comparison between the two contexts, we hope to raise awareness of this new role of teachers among policy makers (O'Meara et al., 2015), thereby ultimately contributing to the endeavour of developing an agreed-upon definition of teacher leadership among stakeholders (Kajitani, 2015) in the Vietnamese context. Finally, in using this framework as a point of departure, we believe that the TLMS would help us recognise where Vietnamese policy makers and educators are in their perception of teacher leadership and from there embarking on expanding opportunities for teacher leadership that help Vietnamese teachers grow to further contribute to the success of our students learning.

Data Collection
In this study, document analysis was adopted to collect 61 national policy documents on professional teacher standards and in-service teacher education. To cover a wide range of national policy documents, two databases including 'Thu vien Phap luat' (Library of legal documents) and 'Van ban Phap luat' (Legal documents), available on the Ministry of Education and Training's website were selected because they provide most relevant and reliable documents related to education in general and teachers in particular.
In terms of the the selection of the documents were followed the 4 steps suggested by Mun et al. (2020) as follows: (1) an initial search using the keywords such as 'teacher,' 'teacher training,' 'teacher professional standard', 'teacher training guidance", "circular on teachers", and "decree on teachers"; (2) A filtering step to remove unrelated documents using two criteria including the policy documents which are not issued by the state government/or Ministry of education because there are many policies which are issued by local governments; and the documents which were issued before 2007 to make sure they are still in effect; (3) identifying the relevance of the documents from the second step by scanning the main content of the documents; (4) an in-depth review of the documents filtered from the previous step. After the 4 steps screening process, we eventually collected 61 documents related to regulations and guidance on teacher professional standards and teacher education.

Data Analysis
In this study, we use the deductive content analysis method to analyze these 61 documents according to the threesteps-procedures suggested by Elo and Kyngäs (2008). Firstly, documents were read as a whole to make sense of the content and contexts in which these documents were made. Secondly, we used the 7 domains with specific functions of the Teacher Leader Model Standards as the structured analysis matrices to code the 61 documents. Accordingly, phrases and words in the documents that correspond to the content of each function listed in the Standards were

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 83  coded and categorized. These documents were coded by two researchers and then cross-checked to ensure reliability. Any differences were clarified and discussed for the final agreement. After finishing this step, the frequency (percentage) of these codes is reported in policy analysis, teacher leadership competence, Vietnam. According to the seven domains in the Standards (see Findings) to answer the research question of the extent to which teacher leadership is manifested in these documents.

RESULTS AND DISCUSSION
Document analysis of 61 documents indicates that all the domains in the Teacher Leader Model Standards were manifested in several documents at different depths.

Domain 1. Fostering a Collaborative Culture to Support Educator Development and Student Learning
The findings reveal that teachers' competency in fostering a collaborative culture at school is stipulated in the documents. The regulations on the professional standard for school teachers and teacher professional development programs require teachers to work with colleagues, students, and parents collaboratively. For example, Circular No. 20/2018/TT-BGDĐT and Circular No. 02/2021/TT-BGDĐT require that to be qualified as "good" teachers, they need to show the ability to support colleagues and students. However, the specific responsibilities to promote the school's collaborative environments are only manifested in several documents. The data shows that using group processes, creating an inclusive culture, and using knowledge and understanding of different backgrounds, ethnicities, cultures, and languages to enhance effective collaboration among colleagues counted for only 11%, while the ability to model effective skills for sharing and developing professional learning was approximately 17.7% (see Table 1). The collected and analyzed documents do not clearly state that teachers need to use "group processes" or model "effective skills" to support colleagues to develop a collaborative working environment. In particular, teachers' reliance on different backgrounds, ethnicities, cultures, and languages to promote effective interactions among colleagues and to create an inclusive culture is also only included in 11% of the documents. This figure may be an indicator of the fact that the role of multicultural education has not been recognized in the Vietnamese education system at the policy level. As such, the lack of regulation on the policies related to developing teachers' collaboration ability to create a collaborative culture at schools could reduce the influence teachers have on their colleagues, the parents, and the students in engaging them in learning and the enactment of their agency in developing teacher leadership.

Domain 2. Accessing and Using Research to Improve Practice and Student Learning
The ability to access and use research to improve teaching and learning is regulated in Circular No. 02/2021/TT-BGDĐT, Circular No. 12/2021/TT-BGDĐT, Circular No.19/2019/TT-BGDĐT, and Circular No. 02/2021/TT-BGDĐT on the professional standard for school teachers and teachers' professional development programs. For example, Circular No. 02/2021/TT-BGDĐT asserts that Level I (the highest level in the teacher professional standard) teachers must "have the ability to evaluate and supervise colleagues in order to research methodology at the district level". It should be noted that the requirements for teachers' responsibilities in doing research are different across education levels (i.e., from primary to secondary) in these documents. However, teachers' specific responsibilities (or functions) related to research are not considered of equal importance, as summarized in Table 2.

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 84  In the Vietnamese context, doing research does not mean to publish in reviewed articles. It can be action research to improve teaching practice. A popular activity is 'sáng kiến kinh nghiệm' (innovative teaching ideas). Accordingly, only 5% of these documents state that school teachers need to support colleagues in collaborating with, for example, higher education institutions in research, particularly in an educational context. Similarly, the ability to support colleagues to collect, analyze, and communicate data from the classroom is counted for 11%. It could be that schools' partnerships with universities have not been well-recognised in Vietnam, resulting in the absence of policies on establishing networks and getting support to and from higher education institutions.

Domain 3. Promoting Professional Learning for Continuous Improvement
Documents on professional standards and levels of professional standards indicate that teachers need to participate in and support colleagues for professional development. For example, Circular No.11/2021/TT-BGDĐT stipulates that teachers need to "participate in professional development based on the teaching practice and collaborate with others in professional development". Notably, there is a big gap among the teacher leadership competencies (or functions) in Domain 3 as demonstrated in the analyzed documents. The requirement of a teacher with the ability to advocate for "sufficient preparation, time, and support for colleagues" and provide "constructive feedback to colleagues" is rarely manifested in the documents, with 3% and 6.5% respectively; while 45% of the documents put the regulations on using technology in professional development (see Table 3).

Table 3. Promoting Professional Learning for Continuous Improvement
Teacher Leaders' Functions Percentage 3.1. Collaborates with colleagues and school administrators to plan professional learning that is team-based, job-embedded, sustained over time, aligned with content standards, and linked to school/district improvement goals; 21% 3.2. Uses information about adult learning to respond to the diverse learning needs of colleagues by identifying, promoting, and facilitating varied and differentiated professional learning; 11% 3.3. Facilitates professional learning among colleagues; 16% 3.4. Identifies and uses appropriate technologies to promote collaborative and differentiated professional learning; 45% 3.5. Works with colleagues to collect, analyse, and disseminate data related to the quality of professional learning and its effect on teaching and student learning; 11% 3.6. Advocates for sufficient preparation, time, and support for colleagues to work in teams to engage in job-embedded professional learning; 3% 3.7. Provides constructive feedback to colleagues to strengthen teaching practice and improve student learning; and 6.5% 3.8. Uses information about emerging education, economic, and social trends in planning and facilitating professional learning. 21% The recognition of the important role of technology in advancing education reflects the common trend of employability in the current society which is faced with a changing technological environment. This regulation is a guideline for teachers' ongoing professional development programs which require teachers to develop their teaching

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 85  career consistently to keep up with the fast pace of changes in technology and its application in education. However, an absence of advocating for time, preparation, and constructive feedback in continuous professional development can be an inhibitor for teachers to engage in these activities in practice.

Domain 4. Facilitating Improvements in Instruction and Student Learning
In Domain 4, two competencies, including working as a mentor, coach, and content facilitator to support colleagues for professional development and serving as a team leader in helping colleagues to respond to the learning outcomes, are stated in a number of documents 19% and 21 % respectively. The roles of teachers, as indicated mostly in the documents, are formal positions such as team leaders. This can be explained by the focus of the leadership roles, which are inevitably made a requisite for school leaders who hold formal leadership positions.

Teacher Leaders' Functions
Percentage 4.1. Facilitates the collection, analysis, and use of classroom-and school-based data to identify opportunities to improve curriculum, instruction, assessment, school organization, and school culture; 9.6% 4.2. Engages in reflective dialog with colleagues based on observation of instruction, student work, and assessment data and helps make connections to research-based effective practices; 0.6% 4.3. Supports colleagues' individual and collective reflection and professional growth by serving in roles such as mentor, coach, and content facilitator; 19% 4.4. Serves as a team leader to harness the skills, expertise, and knowledge of colleagues to address curricular expectations and student learning needs; 13% 4.5. Uses knowledge of existing and emerging technologies to guide colleagues in helping students skilfully and appropriately navigate the universe of knowledge available on the Internet, use social media to promote collaborative learning, and connect with people and resources around the globe; 21% 4.6. Promotes instructional strategies that address issues of diversity and equity in the classroom and ensures that individual student learning needs remain the central focus of instruction. 6.4% Notably, the ability to have reflection sessions or reflective dialogues with colleagues based on observation of instruction, student work, and assessment data to make connections to research-based effective practices (function 4.2) is explicitly stated in only one document (Documentary No. 1315/BGDĐT-GDTH), accounting for 0.6%, the least among six functions of domain 4. This indicates that sharing teaching innovation by conducting action research is not prioritized at the policy level. Doing research is only required when teachers are considered to be promoted. As a result, students' learning success may be negatively impacted because it is evident that there is a positive relationship between cultures of collaboration and professional inquiry with student learning improvement (Waters et al., 2008).

Domain 5. Promoting the use of assessments and data for school and district improvement
Among the four specific competences of Domain 5, competence 5.3 is realized in only one document out of the 61 documents. Even so, that document only states the general sense of the competence, such as "share experience, guide and support colleagues to implement the programme and planning in kindergarten education" and does not contain the sense of building "a climate of trust and critical reflection in order to engage colleagues in challenging conversations about student learning data that leads to solutions to identified issues". As can be seen in Table 5, each of the other 3 competencies is manifested in no more than 18% of the documents. The highest one is competence 5.2, which is stated in 11 documents, taking 17.7 %; next is 5.1 with 12.9 %, and the lowest is 5.4 with only 11.3%. However, even though these three competencies are mentioned in some documents, the ability to support colleagues is stated in only one document. Other documents just show the students' competence in doing their jobs by themselves without supporting or guiding their colleagues. Domain 6. Improving outreach and collaboration with families and the community Among the 5 specific competencies in Domain 6, 6.1 and 6.5 receive more attention from policy makers than the others, with 16 documents for each (25.8%). These 2 competencies emphasize the knowledge and practice of communicating and working with students' families and the community in general in order to enhance the quality of education. For us, the readiness to share knowledge of rearing children with students' families and the community is the realization of leadership among pre-service teachers. However, the ability to facilitate colleagues' self-examination of their own understanding of community culture and diversity and how they can develop culturally responsive strategies to enrich the educational experiences of students and achieve high levels of learning for all students (competence 6.3) is not stated in any document. It can be drawn from the fact that the ability to help colleagues to be able to activate their own knowledge is not the focus of the outcome standards of in-service teachers.

Domain 7. Advocating for student learning and the profession
In this domain, all the 5 competences are mentioned in the 61 documents that were investigated, in which 7.1 is realized in 19 papers (30.6%). This competence takes the second highest percentage (after 3.4) of all the competences throughout the seven domains. However, in almost all of the 19 documents that deal with this competence, there is a focus on the pre-service teachers' ability to use information and knowledge relating to local or state policies and orientation in enhancing the quality of education; there is only one document -the Class II primary school teacher training programme -dealing with the competence of helping colleagues to use such information and knowledge in education, which is, for us, considered as having the quality of leadership.

Teacher Leaders' Functions
Percentage 7.1. Shares information with colleagues within and/or beyond the district regarding how local, state, and national trends and policies can impact classroom practices and expectations for student learning; 30.6% 7.2. Works with colleagues to identify and use research to advocate for teaching and learning processes that meet the needs of all students; 6.4% 7.3. Collaborates with colleagues to select appropriate opportunities to advocate for the rights and/or needs of students, to secure additional resources within the building or district that support student learning, and to communicate effectively with targeted audiences such as parents and community members; 17.7%

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 87  7.4. Advocates for access to professional resources, including financial support and human and other material resources, that allow colleagues to spend significant time learning about effective practices and developing a professional learning community focused on school improvement goals; 8.1% 7.5. Represents and advocates for the profession in contexts outside of the classroom. 8.1% Function 7.3 is the second highest in this domain with 17.7%, but in a similar vein, only 2 documents, namely the Circular stipulating codes, standards for professional titles and appointment and ranking of teach staff in public primary school and the Class IV primary teacher training programme, raise the issue of "helping colleagues fulfil their teaching plans and collaborating with colleagues, parents and community to enhance the education quality".

Discussion
To have an overview of the manifestations of the 7 domains identified by the Teacher Leaders Model Standards in the 61 policy documents, we provide the mean and median scores of each leadership domain in Table 8 below. According to Table 8, it can be observed that, firstly, domain 3 scores highest median value (13.5), reflecting the perceptions of policy makers drafting these documents in which the role of continuous professional development is highly regarded and therefore is given more attention to. Meanwhile, improving outreach and collaboration with families and the community does not receive similar attention, manifesting in the lowest median value of this domain (8.05). However, the difference in these two domains' median values is not significant to conclude that there is an imbalance in policy makers' perception concerning these two domains. In addition, the majority of domains score relatively similar mean and median values, implying that each of these domains is covered in a similar proportion in 61 documents. This means that in these documents, most of the domains are given similar attention.
As this study employs the Teacher Leadership Modal Standards, a comprehensive framework to develop and evaluate teacher leadership (Ado, 2016;Consenza, 2015), the fact that all 7 domains are found present with similar proportion in these documents demonstrates that these policy documents have introduced to a more or less extent, a moderately broad picture of teacher leadership competencies. Given the critical influence of these documents on defining professional standards for the teaching profession in Vietnam, it is important to acknowledge the contribution of these policy documents in establishing fundamental benchmarks for Vietnamese teacher leaders.
Nevertheless, it is undeniable that all 7 domains score relatively low mean and median values (as shown in Table  8). This shows that teacher leadership has not gained sufficient ground to be a policy focus of the teaching profession in Vietnam, although it is acknowledged in the literature as having a positive impact on teachers themselves, their colleagues and their students (Friedman, 2011;Hunzicker, 2012;Poekert et al., 2016). This could be a result of the traditional view that leadership roles are required to formal "school leaders", such as principals, homeroom teachers, heads of the curriculum team, or representatives of union associations (Bond, 2011). This means that from policy makers' point of view, leadership competencies only become essential or required conditions for teachers who are prepared to be school leaders.
In addition, as discussed in the finding section, there are uneven distributions among specific teacher leadership functions in each domain. For example, while function 2.1. is covered in 21% of the documents, and function 2.3 in the same domain only accounts of 5%. Similarly, both functions 6.1 and 6.5 account for 25% of the documents, whereas function 6.3 is not mentioned at all. In an extreme case, function 3.4. is given immense attention (45%), while function 3.6 and 3.7 occupies only 3% and 6.5% of the 61 documents, respectively. This disproportionate pattern is found in almost all domains (except Domain 1), indicating that although policy makers have recognized and attempted to foster certain teacher leadership competencies, there remains a lack of a systematic view of teacher leadership at the policy level.
This deficiency is also particularly evident in the negligence of critical competencies for teachers' leadership development and in confusion between teacher and principal leadership demonstrated in the analysed policy documents. Firstly, among the leadership functions that have been neglected in these documents, many of them are related to teachers' ability to engage in reflection and provide constructive feedback to colleagues. Examples of such functions include 3.7. Providing constructive feedback to colleagues to strengthen teaching practice and improve student learning (accounting for only 6.5.%), 4.2. Engaging in reflective dialogue with colleagues based on observation of instruction, student work and assessment data (0.6%), 5.4. Creating a climate of trust and critical reflection in order to engage colleagues in challenging conversations about student learning data (1.6%), and 6.3. Facilitating colleagues' self-examination of their own understandings of community culture and diversity (0%).
Indeed, these functions are essential for teacher professional development generally and for leadership learning specifically. According to Trotter (2006), feedback and reflection are central to adult learning and development. Being distinct but complementary practices (Bates & Morgan, 2018), feedback and reflection are among the key features characterising effective professional development that are strongly associated with gains in student learning (Darling-Hammond et al., 2017). While feedback is a powerful tool that helps form the basis for critical reflection (Daniel et al., 2013) and strengthens teachers' self-assessment (Fullan, 2006;van Diggelen et al., 2013) of their current understanding, reflection on teaching practices results in improvement of awareness and increases teaching effectiveness (Khazaeenezhad et al., 2018). Hence, without feedback and reflection, teacher professional development in general and teacher leadership learning in particular become ineffective and unsustainable.
Secondly, it is also revealed that these policy documents have not successfully differentiated between teacher and principal leadership. Specifically, although these policy documents emphasise the need of teachers' supporting other colleagues in various activities inside and beyond schools, the focus of the relationship is regrettably not on working together or collaborating. As indicated in the findings, functions that highlight the need of teachers' supporting each other receive particular attention from policy makers, such as 2.1. Assisting colleagues in accessing and using research in order to select appropriate strategies to improve student learning (accounting for 21%), 3.1. Collaborating with colleagues and school administrators to plan professional learning that is team-based, job-embedded, sustained over time, aligned with content standards, and linked to school/district improvement goals (21%) and 7.1. Sharing information with colleagues within and/or beyond the district regarding how local, state, and national trends and policies can impact classroom practices and expectations for student learning (30.6%). However, an in-depth analysis of these documents reveals that the common vocabularies used to describe these teacher competencies as rather being able to 'instruct' or 'help' colleagues. Across the 61 documents, we found only three times the phrase 'collaboration with colleagues' is explicitly mentioned.
As discussed previously, these policy documents may reflect Vietnamese policy makers' traditional view of leadership roles being exclusively designated for teachers who are prepared to be school leaders. Thus, we believe that the vocabularies used to describe the way teachers are expected to work with each other in these documents reflect how strongly the Vietnamese policy makers' perceptions of educational leadership are influenced by the Confucian-oriented principals' leadership styles . However, these principal leadership styles, namely authoritarian (imposing principals' viewpoints over others) and moral (demonstrating standards in moral authority) styles , starkly contrast to teacher leadership as reported in the literature. Accordingly, teachers enact leadership by collaborating (Huang, 2016;Yow & Lotter, 2016) and facilitating other colleagues (Gigante & Firestone, 2008;Hunzicker, 2012) via formal and informal strategies (Poekert et al., 2016) such as sharing ideas and resources (Collinson, 2012) and modelling practices (Fairman & Mackenzie, 2015). Consequently, we argue that there is a confusion between principal and teacher leadership in the perception of Vietnamese policy makers as reflected in these documents. It is critical to differentiate between these two concepts in these documents concerning teaching professional standards because, without such distinction, Vietnamese policy makers may fail to recognize and nurture teacher leadership competencies among teachers.

CONCLUSION
In this study, we have examined the concept of teacher leadership manifested in national policy documents on the teaching profession in the Vietnamese context based on the Teacher Leadership Model Standards as the conceptual framework. The findings reveal that these policy documents have presented a broad but incomplete view of teacher leadership. Percentage-wise, teacher leadership is far from a salient manifestation within policy documents, indicating that it has not yet been considered a core competence in the teaching profession at the national policy level. In addition, there are crucial aspects of teacher leadership that have been neglected, while a lack of differentiation between teacher and principal leadership still remains in the documents.
By implication, the evidence in this study first and foremost suggests that there should be an in-depth and systematic understanding among Vietnamese policy makers about teacher leadership development (i.e. through feedback and reflection) and enactment (i.e. through collaboration). From this understanding, they should incorporate aspects of teacher leadership competencies in educational policy documents. As the policy documents included in this analysis play a crucial role in establishing professional standards for the teaching profession in Vietnam, they strongly influence the design, implementation and evaluation of teacher professional development. The neglect of the above-mentioned leadership aspects in these documents may misguide teacher education institutions, professional learning providers and teachers themselves, thereby hindering the healthy development of the teacher body generally and of teacher leaders particularly.
More specifically, the following recommendations are put forward: 1) Teacher leadership should be considered a core component for teacher development at the policy level. There should be leadership standards for all teachers, both with and without an official management status; 2) A systematic framework for teacher leadership should be developed to be a policy focus for the teaching profession in Vietnam. This framework can be developed either in the form of a separate document exclusively for teacher leadership or being integrated into documents on teachers' standards; 3) Based on such a framework to be outlined at the policy level, teacher leadership should become a criterion for designing, developing, updating, and accrediting teacher education and teacher professional development programs. Especially leadership training should be considered an essential component of initial teacher education (King et al., 2019;Turnbull, 2005) to better prepare pre-service teachers with the necessary knowledge and skills for them to effectively enact leadership in the future. Doing so will enable all teachers to have opportunities to develop their leadership skills, which in turn, will contribute to the development of the schools and the education system.

Conflict of Interest:
No potential conflict of interest relevant to this article was reported.