Attending preschool produces short-term and long-term benefits for children and benefits to communities that outweigh the costs of providing those programs (e.g., Barnett & Masse, 2007; FPG Child Development Institute, 2005; Lamb & Ahnert, 2006; Lazar, Darlington, Murray, Royce, & Snipper, 1982; Reynolds, 2000; Reynolds, Temple, Robertson, & Mann, 2001; Schweinhart, Barnes, & Weikart, 1993). The ability to realize these benefits for children and communities depends in part on whether preschool programs are designed and structured in ways that maximize opportunities for children to learn and develop within these settings. Policy makers are currently debating decisions to invest in specific program features intended to optimize outcomes for children, such as requiring teachers to have a bachelor's degree or specialized training in early childhood education, mandating small class sizes, adopting intensive professional development programs, and instituting systems of program quality monitoring. These decisions have implications for both the costs of providing preschool programs and the benefits for children who attend.
To help inform decision making about the optimal design of preschool settings, a generation of experimental and natural-history studies about preschool quality clearly demonstrates that variations in how programs are structured have consequences for children's physical and psychological well-being and development of social and academic competencies (e.g., Howes, 1990; NICHD-Early Child Care Research Network (ECCRN), 1999, 2002; Peisner-Feinberg & Burchinal, 1997; Peisner-Feinberg et al., 2001).