This article describes the contributions of cognitive-scholastic advantage, family support behavior, and school quality and support as processes through which early childhood interventions promote well-being. Evidence in support of these processes is from longitudinal cohort studies of the Child-Parent Centers and other preventive interventions beginning by age 4. Relatively large effects of participation have been documented for school readiness skills at age 5, parent involvement, K-12 achievement, remedial education, educational attainment, and crime prevention. The three processes account for up to half of the program impacts on well-being. They also help to explain the positive economic returns of many effective programs. The generalizability of these processes is supported by a sizable knowledge base, including a scale up of the Child-Parent Centers. (author abstract)