Over the last decades, schools as organizations in many countries have become more complex including enlargement of scale (and thus additional layers in the organizational structure) and increased responsibilities to develop local policies (Piot & Kelchtermans, submitted), bringing with them new issues of management and leadership, as well as often dramatic shifts in organizational cultures, differentiation of professional roles and responsibilities for staff members, etc. The latter is often referred to as the emergence of “teacher leadership” (although it is obvious from the international literature that this concept has broad and diverse meanings) (see a.o. York-Barr & Duke, 2004; Smylie & Mayrowetz, 2009). We use as a working definition of teacher leaders any teacher who is given the formal mandate to take on responsibilities of leading other members of the teaching staff and enacts these responsibilities, while still – part time – remaining  a classroom teacher. The leadership tasks and responsibilities can be temporary or more structurally embedded.

The appearance of teacher leadership roles and –as a consequence- people who enact these roles changes the traditional division of roles between teachers and leaders in schools and the social networks in the teaching staff (Kelchtermans, 2006). As such it constitutes a challenging agenda for research and theory development in that it demands more complex theories about leadership as well as about the roles and social relations among members of a school staff. Eventually the issue at stake is that of teachers’ professional ‘identity’ or self and its development throughout the career as they take on teacher leadership roles. Yet, this development is strongly influenced by the interactions with colleagues on the one hand and formal leaders on the other.

The research reported on in this paper builds on former work on teacher development from a narrative-biographical (including social-constructivist, interactionist and contextualized stances) and micro-political perspective (Kelchtermans, 1993, 2004, 2007; Piot & Kelchtermans, submitted; Kelchtermans, Piot & Ballet, 2011;). It was further inspired by the critical questions Smylie and Mayrowetz (2009) recently raised on teacher leadership and its impact on the individual teacher (leader) as well as the organizational culture and school reform.

The central research questions for this exploratory study are:

• How is teacher leaders’ sense-making of their professional role embedded in and influenced by their professional biography as teachers?

            - How do they (re)define their own sense of professional self in the new role?

            - How do they evaluate the teacher leader position (benefits, threats)?

• What are the perceived consequences of taking on teacher leadership roles for the social relationships between the teacher leader and the teachers and between the teacher leader and formal school leader?

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