Forty years of research have convinced scholars and policy makers that quality preschool experiences benefit children from impoverished environments and help prepare them for school entry (see reviews by Barnett, 1995; Brooks-Gunn, 2003; Frede, 1995; Haskins, 1989; National Research Council, 2000, 2001; Yoshikawa, 1995). Yet public preschool programs for disadvantaged children remain sparse and underfunded. Although the United States was among the first industrialized nations to offer 12 years of free public education to rich and poor alike, it still does not ensure that poor children receive the preschool experience necessary to get ready for school. Despite our democratic ideals, nonpoor children in the United States have greater access to quality preschool programs than those whose families have less money. Indeed, evidence indicates that the most at-risk children are the least likely to attend preschool (Hofferth, West, Henke, & Kaufman, 1994; West, Hausken, & Collins, 1993).
In 1965, as part of the Johnson administration's War on Poverty, the federal government created a nationwide, community-based preschool intervention to promote school readiness among economically disadvantaged children. Since its inception, Head Start has grown from a six-week summer school to an academic-year program that by now has served more than 22 million preschoolers and their families (U.S. Department of Health and Human Services, 2005). To be eligible for Head Start, children must live in homes that are below the federal poverty threshold ($18,244 for a family of four in 2002).