The CSUN NSF Teaching Fellowship Program represents a partnership among California State University Northridge, the Los Angeles Unified School District (the second largest district in the nation), and the non-profit Art Center College of Design. The partners are working together to develop and retain eleven Teaching Fellows and five Master Teaching Fellows who will be secondary mathematics teachers able to lead efforts to improve mathematics instruction in their schools and districts. The Fellows are participating in courses and professional development activities that are designed to meet the needs of professionals teaching in high-need, urban settings. The goals of the project include providing Fellows with professional development opportunities such as mentoring, summer workshops, and in-service activities, increasing achievement of students as measured by their Academic Performance Index scores, and improving the long-term retention of the Fellows. The Master Teaching Fellows are providing leadership in the supervision of student teachers who are employing research-based pedagogies. The project is being rigorously assessed to determine the impact of the program on the Fellows' content knowledge, instructional practices, and attitudes about teaching and learning and ultimately the impact of the program on the attitudes and achievement of the students they teach.