The Child Development Project (CDP) is a school-based program designed to foster children's social, ethical, and intellectual development through activities emphasizing cooperative learning, developmental discipline, social understanding, interpersonal helping, and prosocial values. The CDP was implemented in kindergarten through fourth grade by regular classroom teachers with a cohort of students who began kindergarten in fall 1983 in three northern California elementary schools. At one of the schools, CDP continued through grade 6. Students from two CDP and two comparison schools entered the same intermediate school, where long-term effects of the program were assessed. In kindergarten and grades 2, 4, and 8, individual interviews with the CDP and comparison students were conducted to assess certain social skills, inclinations, and values. In addition, group questionnaires were administered in grades 7 and 8. Study findings indicated that the program had some sustained effects on children's social development. Conflict resolution, which had shown strong effects in earlier years, maintained this effect in the eighth grade. Two moral reasoning variables concerned with helping and responding to transgressions showed a small effect when combined across years. Self-esteem, which had not shown an effect when last assessed in elementary school, showed a quite strong effect in eighth grade. Finally, the program's effect on democratic values, which was significant in grade 4, disappeared by grade 8. (AC)