An insightful inside perspective on the implementation of instructional improvement measures in a large urban K–12 district In When Reform Meets Reality, Jonathan A. Supovitz and contributors examine the qualities that make ambitious educational reforms impactful and identify common tensions that can thwart continuous improvement. Supovitz brings together educational researchers, district and school leaders, teachers, and professional development providers to reflect on the successes and stumbles of an ambitious district-wide reform effort—the Ongoing Assessment Project (OGAP), a program for mathematics education—as it was introduced and scaled up over five years in the School District of Philadelphia. Using OGAP as a lens, the volume explores larger themes of instructional reform, including the potential of new instructional approaches to improve the quality of teaching and learning, the contexts that can either support or hinder efforts to introduce meaningful pedagogical