In 2011, the Bill & Melinda Gates Foundation created the Project Mastery grant program to support competency-based education initiatives in large school systems that serve a high proportion of disadvantaged youth. Competency-based education is education that meets stu- dents where they are academically, provides students with opportunities for choice, and awards credit for evidence of learning, not for the time students spend studying a subject. The grants supported the development and implementation of technology-enabled curricula, online learn- ing management systems, and teacher professional development during the 2011–2012 and 2012–2013 academic years. The three recipient organizations—which included two large school districts and one intermediary organization—carried out their pilot programs in a total of 12 public secondary schools distributed across five school districts in four states. The Foun- dation asked RAND to evaluate these efforts in terms of implementation, students’ experi- ences, and student performance. This report presents final results from that evaluation. It pro- vides an overview of competency-based education and the Project Mastery grant projects and describes the implementation of competency-based educational features under each project. It also reports on student survey data from each of the projects. Finally, it describes the academic performance of students exposed to the sites’ competency-based models relative to similar stu- dents or schools. The report concludes with six lessons for policy, partnerships, and practice. The results should be of interest to educational policymakers and practitioners interested in competency-based education models as an approach to K–12 education reform. This study was undertaken by RAND Education, a business unit of the RAND Corporation, on behalf of the Bill & Melinda Gates Foundation.