Research suggests a strong association between the existence of professional learning communities within schools, increases in the effectiveness of practice, and improvement in student achievement. This paper describes the National School Reform Faculty (NSRF), a professional development program at the Annenberg Institute for School Reform at Brown University. It is based on three assumptions: the new paradigm of professional development provides the best way for school people to make changes required by the new expectations for teaching; professional learning communities can be deliberately created and sustained by people inside the schools; and training and support can reduce the fragility of collegial structures. All schools within a Coalition of Essential Schools were invited to join, and 75 schools with 90 Critical Friends Group (CFG) coaches were accepted. Participants committed themselves to working in small CFGs of faculty and administrators toward self-defined goals for improved student learning. The Annenberg Institute committed itself to training and supporting coaches. Despite variability among CFGs, there were common developmental stages, including considering the CFG an oasis where educators could collaborate with colleagues; using member time to strengthen approaches to teaching and strengthen understanding of how students learn; and addressing fundamental questions about teaching. Factors that were influential in helping or inhibiting CFGs from moving to more complex levels included internal group dynamics, administrative structure, school culture, and access to resources. (Contains 16 references.) (SM)