The Instructional Leadership Corps (ILC) is an innovative professional learning network in which teacher leaders in California collaborate and support their colleagues in developing teaching strategies and practices aligned with new content standards. Over more than 4 years, 100,000 teachers have participated in conferences and trainings, with overwhelmingly positive responses. 

This study describes how the ILC has changed the professional development landscape in four districts, offering lessons about how teacher-led learning can motivate shifts in practice, enhance teachers' professionalism and efficacy, and create supportive systems and strategic relationships that can sustain change.