The purpose of this study was to understand what promotes or hinders the implementation of a high school education reform policy in Arizona schools from the perspective of a nonprofit organization that served an active and intentional role as an intermediary organization working directly with schools and policymakers. The study was intended to facilitate implementation of the education reform policy in the school sites, to gain knowledge that will be used to inform future cycles of planning and implementation, and to influence state policy. This study was an explanatory nonexperimental multiple case study involving five high schools across Arizona. The study focused on the early phase of implementation of the education reform policy. A mixed methods case study design grounded in the tradition of participatory action research was employed. Data were collected through surveys, interviews, observations, focus groups, and a document review. The results suggest that the education reform policy was implementable in diverse schools across the state. However, how the education reform policy was implemented in each school site appeared to vary. A number of factors seemed to influence the actual implementation process including the design and understanding of the reform, selection process, district context and school characteristics, and school capacity to undertake the reform. The findings suggest that the nonprofit organization that served as an intermediary organization within the study influenced the implementation process. It appears that this primarily took place by providing direct assistance to the schools, creating opportunities for collaboration and communication across the multiple school sites implementing the same education reform policy, and serving as a connector to other organizations, policymakers, and the larger public. The study resulted in the nonprofit organization's deeper understanding of the complexity of implementing the education reform policy, the challenges schools face in implementing the reform, and the factors that appear to promote or impede the implementation process.