Building on evolving conceptions of teacher leadership in the literature, this article argues that an integration of both positional and empowering elements of teacher leadership are the seeds of an evolved approach to teacher leadership for instructional improvement. Using data from a study of quasi-formal teacher leadership, the research examines how teacher leaders play a positive role in schools and fulfil a series of needs of teachers. However, the constraints of teacher leaders' instructional authority limits their ability to influence the instructional practices of their peers. The findings clarify the distinction between school-level and individual-level teacher leadership.