This study intends to take a population-based look at the protective benefit of Head Start in an entire cohort of children who are transitioning into kindergarten in a large, urban school district and who live in a context of multiple early risks to development. There are three primary purposes of the proposed research study. The first is to understand the unique influences of child maltreatment, homelessness, high lead exposure, and low maternal education on academic and behavioral adjustment for an entire cohort of children entering kindergarten. The second purpose is to examine the protective benefits of having a Head Start experience for academic and behavior adjustment among these kindergarten children living in a context of multiple risks. Finally, this study proposes to investigate whether the protective benefit of Head Start is maintained through the end of first grade. The proposed study will analyze a subset of data from a longitudinal study using the Kids Integrated Data System (KIDS). KIDS is designed to integrate data across city agencies for research to inform public policy and practice. This unique capacity allows for population-based epidemiological research that considers the complex contexts in which children and families live.