This study explores the long run effects of alternative certification in a school district. The New York City Teaching Fellows (NYCTF) program has been a major supplier of teachers to New York for over 10 years. Virtually all research on alternative certification examines teachers in the first 2 to 3 years of their careers. In contrast, this research considers the nature of a large alternative certification program as it matures and as the needs of the school district shift. It also explores how the NYCTF has changed the profile of teachers in New York City and the outcomes for students. This research is funded by the Noyce Foundation and is being conducted in collaboration with researchers at Stanford University.