Research Findings: Integrated services for young children and families are part of the new policy landscape in early childhood, but there is limited evidence of the effectiveness of these programs and how they develop on the ground. This study examined the use of the Early Development Instrument (EDI) as both a summative program evaluation tool and as a formative program improvement tool supporting practitioners in Toronto First Duty, an integrated services demonstration project that combined kindergarten, child care, and parenting supports in public schools. Pre-post comparisons at community demonstration sites and comparisons with matched community sites using the EDI suggested that the demonstration program was associated with modest improvements in emotional and social domains of children's development. Mixed methods and multiple measures were used to contextualize summative findings in case studies across demonstration sites. The case studies explored how integration was implemented at different sites and how dimensions of enacted integration might contribute to positive outcomes for children and families. A case study of one site showed how an integrated staff team used EDI school-level profiles, along with formative feedback on program quality, to target and improve programming. Over the course of implementation, the integrated program environment quality ratings and EDI scores improved in relevant areas assessing quality of interaction and social-emotional development. Practice or Policy: Findings are discussed in terms of the role of the EDI in program evaluation and in improvement of practice. The potential value of integrated early childhood services and the challenges of evaluating complex community initiatives are also discussed. (Contains 1 figure.)