In ever-increasing numbers, children in this age group are involved in out-of-home programs, including child care centers, family child care homes, and public or private full- and half-day prekindergartens. In fact, more than half of 3- and 4-year-olds in the United States are enrolled in some type of preschool program (NCES 2008), with public schools serving more than 20 percent of 4-year-olds (Pre-K Now 2008a).