Based on qualitative data collected over a 6-month period, this article examines how teachers' experiences of principal leadership practice influence their capacity to engage in meaningful collegial interactions during structured collaboration. Similar to previous studies, our findings confirm the limitations of leadership that relies primarily on structural changes to foster collaboration. Our findings contribute further to leadership research by presenting teachers' perspectives on why particular principal leadership practices matter to teacher collaboration and by illustrating how the principal's enactment of leadership practices influences teachers' sense of efficacy and motivation, both of which are critical to professional learning during collaboration.

Building on York-Barr and Duke's (2004) conceptual framework for teacher leadership, this article explores teacher leadership as an informal influence that arises out of interactions and is exerted through group processes and norms. Through a 4-month qualitative study of two teacher teams’ work during structured teacher collaboration, we sought to understand how teachers’ informal action and interaction influence their colleagues’ sense of self-efficacy and motivation to engage in collaborative work. Given our findings, we theorize an emergent framework for teacher leadership to promote understanding and future investigation of teacher leadership as an informal, socially distributed phenomenon.