Participants in this session will learn about the efforts of a large comprehensive high school of 3,200 students in New York City to improve student achievement through the creation of nine semi-autonomous thematic institutes, or small learning communities (SLCs). The presenters will use the experience at Hillcrest to explore use of data to plan reform, shifting roles and responsibilities, ways to challenge fragmentation and isolation, and mechanisms for preserving the strengths of large schools without compromising the integrity of the SLCs.