This study proposes an empirically grounded theory of how school reform implementation relates to effectiveness, useful for developing and studying many approaches to school reform both in the U.S. and abroad, and also for assessing how policymakers and implementers might leverage various aspects of implementation to create effective school improvement models at scale. Guided by a new framework that links Bryk and colleagues' (2010) five essential supports and as reported by Desimone's (2002) adaptation of Porter and colleagues' (1986) policy attributes theory, we use a mixed-methods approach to study the implementation and effectiveness of school turnaround efforts in the School District of Philadelphia. We explore the relationships among key turnaround model components, approaches to model implementation, and academic achievement using a matched comparison design and estimating a series of regressions. Qualitative methods are used to contextualize findings and offer explanatory hypotheses.