As part of the Longitudinal Study of Children at Risk, this study evaluated the Child Parent Center (CPC) Program, a preschool to third grade intervention program funded by the Elementary and Secondary Education Act (ESEA) Chapter I. Subjects were 915 low-income black children from 20 inner-city schools who were differentially exposed to school-based, comprehensive service components for up to 6 years. The comparison group consisted of 191 children who received only an all-day kindergarten program. The following six outcomes, measured in grades three through five, were used to evaluate the effects of the program: reading achievement; mathematics achievement; teacher ratings of school adjustment; parental involvement; special education placement; and grade retention. Results indicated that the duration of intervention was significantly associated with all outcomes. Analysis of seven intervention and comparison groups differentially exposed to the intervention revealed that children participating in full intervention through third grade or participating in the intervention through second grade were the only children who consistently outperformed the comparison group on the outcome variables, notably for grade retention, reading, and mathematics achievement. Results support the value of extended early childhood intervention programs with at-risk children. (MM)