The purpose of the 3-year evaluation study was to assess the effectiveness of the Ounce PDI in advancing the knowledge, skills, and dispositions of community-based early childhood leaders and teachers in relation to creating the conditions for superior developmental outcomes and kindergarten readiness for low-income, under-served students served by these community-based centers. Therefore, the evaluation pursued three broad goals: First, we intended to monitor and summarize patterns of implementation over the full span of the PDI in order to assess fidelity and feasibility of implementation. Second, we aimed to assess impacts of implementation on the professional learning of teachers, leaders, and coaches, and more distally, upon the growth and development of children in all intervention centers. Third, drawing on Improvement Sciences methodology, we planned to strike a productive balance between the roles of independent, external summative evaluator, on the one hand, and collaborative formative evaluator providing rich and timely data and feedback to the design development process. (author abstract)