The state of preschool evidence: a review of (quasi) experimental research

• In Event: Educational Environments and Child Development in Low-Income Contexts

Abstract

Multiple disciplines have undertaken studies examining the impacts of increased access to center-based preschool and changes in preprimary classroom practices, and these studies have used data from high-, middle-, and low-income countries. This paper describes the state of experimental and quasi-experimental research on center-based preprimary education, with a focus on identifying evidence gaps for future research in low-income countries.

Using keyword searches in research databases, as well as expert recommendations, we first identified 265 studies that estimated impacts of center-based care that aimed to impart education services for preprimary children between the ages of 3 and 6 and that were published in peer-reviewed journals or working paper series. We further screened these studies to identify those that could credibly estimate causal impacts of preprimary interventions on preprimary coverage, caregiver behavior, or child development and any subsequent indicator that could proxy for a dimension of wellbeing in adulthood. From each of the included studies, we extracted information on three levels: study, intervention (contrast) and outcome (measurement domain and effect size). The resulting sample includes 56 studies, 150 intervention contrasts, and 604 outcomes.

Most studies use data from high-income countries, with over half from the United States and Canada. Split roughly evenly across the disciplines of Economics and Education and measuring multiple domains of child development and adult well-being, these studies tend to be randomized control trials of programs that had targeted a disadvantaged population. Most studies present results measured during the pre-primary period, while close to half report estimates of outcomes measured while children are attending basic education, and 11 percent report impacts measured in adulthood. No study in a middle- or low-income country estimates impacts beyond the early primary years, and the focus of these studies has mainly been on the impacts of expanding coverage rather than the effectiveness of different curricular or pedagogical approaches. Just over half of the studies report any costs of the evaluated interventions. Perhaps because of our focus on studies published in journals and formal working paper series, the distribution of effect sizes and precision of included studies are suggestive of publication bias.

As the (quasi) experimental literature on preschool continues to grow, particularly in low-income countries, it will be important to design well powered studies that allow children to be followed longitudinally. Given the rapid expansions of preschool coverage that are already happening in these contexts, it will also be important to shift the focus of research to testing ways to improve the quality of services and expand our understanding of how different elements of quality early childhood education can interact to improve child outcomes.

Authors

• Alaka Holla, World Bank - District of Columbia
  Presenting Author

• Maria Magdalena Bendini, The World Bank
  Non-Presenting Author

• Lelys Dinarte, The World Bank
  Non-Presenting Author

• Iva Trako, World Bank
  Non-Presenting Author