Comprehensive school reform (CSR) took hold across the United States during the 1990s. Its aim is to improve a school—the primary unit of change— by applying effective practices in every area, including curriculum and instruction, assessments, parent and community involvement, professional development, and school and classroom management. Key to the success of this effort is the support of school design teams, also known as CSR model providers, whose purpose is to help existing K-12 schools transform themselves into high-performing organizations through “whole-school designs.” This entry describes the early development of CSR designs with the support of the New American Schools Development Corporation (NAS), the research on the implementation and effects of CSR designs, the support of CSR by the federal government, and the future of ...