This study was designed to fill the "implementation measurement" gap. A methodology to quantitatively measure the level of Comprehensive School Reform (CSR) implementation that can be used across a variety of CSR models was developed, and then applied to measure actual implementation of four different CSR models in a large number of schools. The study also compared the extent to which actual practices in curriculum, instruction, governance, grouping of students, assessment of students, and parent involvement differed between schools using these four models and a sample of matched comparison schools that did not use the models. Previous research on CSR implementation has relied mainly on in-depth case studies. Although this approach can provide good data, it is expensive, resulting in studies that focus on only a small number of schools. The methodology developed for this study has two advantages. First, it relies primarily on surveys of principals and teachers supplemented by a small number of case studies, and therefore can be used for a large number of schools at a time. Second, it is applicable to all types of CSR models and can also be used to study practices in nonmodel schools. This approach involves, first, the acquisition of an in-depth knowledge and understanding of the model's philosophy and core components (for most models, core components include curriculum, methods of instruction, governance, student groupings, assessment, and parent involvement). Second, a detailed understanding of each model was translated into a set of practices or activities that the school should have or do in order in order to implement the core components. (Contains 45 tables, 3 figures, and 10 appendixes.) [The research described in this report was conducted within RAND Education.]