This study investigated the impact of differential programming on urban, low income black children's early school achievement. The 728 children in the study, all residents of the Bedford-Stuyvesant and Brownsville areas of Brooklyn, N. Y., were "graduates" of 17 preschool programs during 1967, 1968, and 1969. The programs included 6 licensed, developmental day care centers; 4 unlicensed, custodial day care programs; 4 Head Start Centers; and 3 Board of Education Early Childhood Centers and prekindergarten programs. Specific information about each of the programs was obtained from a retrospective interview schedule and included program objectives, facilities, staff, curriculum, parental involvement, and ancillary data. Data collected from elementary school records included demographic information (particularly birthplace and family characteristics), school attendance, personal/social behavior, physical/health status, and school achievement as measured by the Metropolitan Achievement Test and the Reading and Mathematics Test for New York State Elementary Schools. The results strongly suggest that children from licensed day care programs are performing better than their peers during the early school years. Specific results and data limitations are discussed in detail. (ED)