Jan 31 2019

Untangling the Evidence on Preschool Effectiveness: Insights for Policymakers

This report adds to the growing consensus that the preponderance of evidence demonstrates that high-quality preschool leaves children better prepared for school, especially in terms of their academic skill development.

It includes reviews of rigorous evaluations of 21 public preschool programs, finds that students who attend high-quality preschool programs reap benefits that can last throughout their lives, and are more prepared for school and experience substantial learning gains in comparison to children who do not attend preschool.

Research on early learning programs in the 1960s and 1970s revealed that enormous benefits for children lasted into adulthood, inspiring many states to invest in preschool programs. However, recent evaluations of two programs—Tennessee’s Voluntary Pre-K program and Head Start—found mixed results, leaving policymakers and the public confused about whether or not investments in preschool programs actually do make a difference to student success. This report reviews these two studies and others in depth, noting that interpretations of the results often depend on the groups of students being compared.  When participants are compared to very similar students who did not attend preschool, the benefits of participation are typically found to be substantial.  Both preschool and elementary school quality also make a difference for the strength of ongoing effects in terms of achievement, school progress, and attainment. 

The report finds that investments in quality preschool programs bolster student success. Students who attend preschool programs are more prepared for school and are less likely to be identified as having special needs or to be held back in elementary school than children who did not attend preschool. Studies also show clear positive effects on children’s early literacy and mathematics skills.

It examines research on programs that succeed in preparing children for school identifies important elements of quality. Those elements include

  • sufficient learning time and small class sizes with low student-teacher ratios;
  • well-prepared teachers who provide engaging interactions and classroom environments that support learning;
  • ongoing support for teachers, including coaching and mentoring, with program assessments that measure the quality of classroom interactions and provide actionable feedback for teachers to improve instruction;
  • research-based, developmentally appropriate early learning standards and curricula;
  • assessments that consider children’s academic, social-emotional, and physical progress and contribute to instructional and program planning; and
  • meaningful family engagement.

Most or all of these elements are present in the programs that demonstrate the strongest and most persistent impacts on children. The research also indicates that to determine the full benefits of an effective preschool program, one must look beyond the preschool years. A year or two of even the highest quality program cannot inoculate children from the detrimental effects of living in impoverished communities and experiencing poor elementary or secondary schooling. Moreover, studies of preschool programs that have followed students into adulthood find up to $17 returned in social benefits for every dollar invested. This is because people who attend preschool are less likely later on to be unemployed or incarcerated and more likely to graduate high school and earn higher salaries. Even when students are only followed into elementary school, there are significant benefits from preschool in lower rates of grade retention and special education placements. These benefits produce an average of $2 to $4 returns on the dollar. High-quality preschool programs can also help close the gap in school and life outcomes between those raised in low-income families and their wealthier peers.

The quality of early learning is important for immediate outcomes, but sustained benefits likely require more comprehensive investments in children and their families.

Although studies vary, there is growing evidence of long-lasting benefits for children’s school progress and behavioral outcomes. The consistency of conclusions and those of other scholars affirms their robustness and underscores the importance of communicating the evidence effectively to a broad audience. Rather than continuing to debate whether to invest in preschool, policymakers should focus their attention on understanding what must happen in a preschool classroom and the k–12 school system to ensure their investments pay off.


Untangling the Evidence on Preschool Effectiveness: Insights for Policymakers by Beth Meloy, Madelyn Gardner, and Linda Darling-Hammond is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

This research was supported by the Heising-Simons Foundation. Core operating support for the Learning Policy Institute is provided by the Sandler Foundation, the Hewlett Foundation, and the Ford Foundation.