The Evidence on Universal Preschool
Calls for universal preschool programs have become commonplace, reinforced by President Obama’s call for “high-quality preschool for all” in 2013. Any program that could cost state and federal taxpayers $50 billion per year warrants a closer look at the evidence on its effectiveness.
A review of the major evaluations of preschool programs—including both traditional programs such as Head Start and those designated as “high quality”—does not paint a generally positive picture.
Before policymakers consider huge expenditures to expand preschool, much more research is needed to demonstrate true effectiveness.
The most methodologically rigorous evaluations find that the academic benefits of preschool programs are quite modest, and these gains fade after children enter elementary school. Meanwhile, most contemporary “high-quality” preschool programs have been evaluated using a flawed, non-experimental methodology that fails to account for children who drop out of treatment groups, thereby biasing outcomes upwards. Furthermore, these evaluations cannot assess the fadeout problem because all children studied—both treatment and control—have taken preschool.
Two “high-quality” programs have been evaluated using a rigorous experimental design, and have been shown to have significant academic and social benefits, including long-term benefits. These are the Abecedarian and Perry Preschool programs. However, using these two studies as the basis for policy is problematic for several reasons: the groups studied were very small, they came from single communities several decades ago, and both programs were far more intensive than the programs being contemplated today.
