Preschool interventions are arguably one of the most important elements of support for poor families. Head Start, a federal program for children in low-income families administered through the Department of Health and Human Services, is a case in point. While research shows a range of benefits lasting beyond preschool for participants, evidence of the “fade-out” of cognitive gains of the preschool years and the differential impact of the program on children with different skill levels in the preschool population has prompted debate over its efficacy.