Objectives of this study were (1) to determine the effect of preschool experience on the personal and social adjustment and school readiness and achievement of the deprived child, (2) to determine what combination of age at intervention and treatment intensity was most effective, and (3) to assess the effects of parent involvement on the child's academic performance. Phase I tested children in the Preschool Readiness Program, summer Head Start children, low income children without preschool experience, and middle income children who entered first grade in September, 1967. Phase II consisted of experimental and control groups who entered first grade in September, 1968. Results of the Metropolitan Readiness Test and the Peabody Picture Vocabulary Test showed that disadvantaged children who participated in the Preschool Readiness Program were better prepared to compete with children without such experience. This was confirmed for both Phase I and Phase II, and both phases made significant gains on the PPVT. Phase I children made significant gains on the MRT, but middle income children scored highest in Phase II. There was no significant change in personal adjustment. Children whose parents were actively involved showed greater achievement. (DR)