Early educational intervention has been proposed to partially offset the impacts of poverty and inadequate learning environments on child development and school success. A broad range of early educational interventions are found to produce meaningful, lasting effects on cognitive, social, and schooling outcomes. However, all interventions are not equally effective. Two major U.S. programs perform relatively poorly. Research provides some guidance regarding the features of highly effective programs, but much remains to be learned. New experimental studies of key program features would have a high payoff.