What is the cost of a preschool program ?

State and local governments that wish to establish or improve preschool programs need cost estimates to evaluate the magnitude of appropriations required. Yet even a casual scrutiny of available expenditure data reveals an enormous variance between the most expensive and least expensive preschool provisions. The purpose of this paper is to delineate the root causes of differences in per-student costs of states' preschool programs and to suggest cost tradeoffs as different features such as smaller class size or longer school days are introduced or substituted for each other. These cost findings are contrasted with recent meta-analyses of the effectiveness of different program provisions. The goal of this paper is to advance the still nascent body of research on preschool cost effectiveness, and to aid state or local governments to assess the mix of characteristics that are most effective for any given budget constraint. The paper builds partially on the authors' previous analysis of international preschool programs.