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Full-Day Versus Half-Day Preschool
February 2021


"What does the research say about full-day versus half-day school-based preschool programs?"

Ask A REL Response

Thank you for your request to our Regional Educational Laboratory (REL) Reference Desk. Ask A REL is a collaborative reference desk service provided by the 10 RELs that, by design, functions much in the same way as a technical reference library. Ask A REL provides references, referrals, and brief responses in the form of citations in response to questions about available education research.

Following an established REL Northwest research protocol, we conducted a search for evidence- based research. The sources included ERIC and other federally funded databases and organizations, research institutions, academic research databases, Google Scholar, and general Internet search engines. For more details, please see the methods section at the end of this document.

The research team has not evaluated the quality of the references and resources provided in this response; we offer them only for your reference. The search included the most commonly used research databases and search engines to produce the references presented here. References are listed in alphabetical order, not necessarily in order of relevance. The research references are not necessarily comprehensive and other relevant research references may exist. In addition to evidence-based, peer-reviewed research references, we have also included other resources that you may find useful. We provide only publicly available resources, unless there is a lack of such resources or an article is considered seminal in the topic area.


Atteberry, A., Bassok, D., & Wong, V. C. (2019). The effects of full-day prekindergarten: Experimental evidence of impacts on children’s school readiness. (EdWorkingPaper: 19-79). Providence, RI: Annenberg Institute at Brown University. Retrieved from

From the Abstract:
"This study is a randomized control trial of full- versus half-day pre-kindergarten in a school district near Denver, Colorado. Four-year-old children were randomly assigned an offer of half-day (four days/week) or full-day (five days/week) pre-k that increased class time by over 600 hours. The offer of full-day pre-k produced substantial, positive effects on children’s receptive vocabulary skills (0.267 standard deviations) by the end of pre-k. Among children enrolled in district schools, full-day participants also outperformed their peers on teacher-reported measures of cognition, literacy, math, and physical development. At kindergarten entry, children offered pre-k still outperformed peers on a widely-used measure of basic literacy. The study provides the first rigorous evidence on the impact of full-day preschool on children’s school readiness skills."

Freedberg, L., & Frey, S. (2017). Expanding early learning time: Accessing full-day preschool and kindergarten in California. EdSource.

From the Abstract:
"Compelling research shows that attending high-quality, full-day preschool and kindergarten is associated with improved outcomes for students. These outcomes include greater school readiness in a number of areas including language development, higher academic performance in math and reading, and less likelihood of being retained in later elementary grades. This EdSource report looks at the status of recent efforts in California to provide more children with access to full-day preschool and kindergarten. In order to move the state toward its expressed goal of encouraging full-day attendance at both preschool and kindergarten, this report also highlights the importance of several key strategies."

Herry, Y., Maltais, C., & Thompson, K. (2007). Effects of a full-day preschool program on 4-year-old children. Early Childhood Research & Practice, 9(2), 1–20.

From the Abstract:
"This study explored the effects of a full-day preschool program on 4-year-old children. The study compared the development of a group of children (N = 403) who attended the preschool program on a half-day basis during the 1999-2000 school year (the last year the half-day program was in place) with the development of a group of children (N = 418) who attended the program on a full-day basis during the 2000-2001 school year (the inaugural year of the full-day program). The instruments used in this study assessed language, academic learning, prosocial behavior, conduct problems, and motor skills, as well as the degree to which parents were satisfied with their children's preschool programs. The results suggest that the full-day preschool program had a positive effect on children's language and academic learning as well as on parental satisfaction with the programming but that the full-day program did not affect prosocial behavior and conduct problems."

Reynolds, A. J., Richardson, B. A., Hayakawa, M., Lease, E. M., Warner-Richter, M., Englund, M. M., ... & Sullivan, M. (2014). Association of a full-day vs part-day preschool intervention with school readiness, attendance, and parent involvement. JAMA, 312(20), 2126–2134. Retrieved from

From the Abstract:
"Importance: Early childhood interventions have demonstrated positive effects on well-being. Whether full-day vs part-day attendance improves outcomes is unknown. Objective: To evaluate the association between a full- vs part-day early childhood program and school readiness, attendance, and parent involvement. Design, Setting, and Participants: End-of-preschool follow-up of a nonrandomized, matched-group cohort of predominantly low-income, ethnic minority children enrolled in the Child-Parent Centers (CPC) for the full day (7 hours; n = 409) or part day (3 hours on average; n = 573) in the 2012-2013 school year in 11 schools in Chicago, Illinois." Results: Full-day preschool participants had higher scores than part-day peers on socioemotional development, language, math, physical health, and the total score. Literacy and cognitive development were not significant. Full-day preschool graduates also had higher rates of attendance and lower rates of chronic absences but no differences in parental involvement.

Robin, K. B., Frede, E., & Barnett, W. S. (2006). Is more better?: The effects of full-day vs. half-day preschool on early school achievement. New Brunswick, NJ: National Institute for Early Education Research, Rutgers. Retrieved from

From the Document:
"Numerous studies demonstrate the positive benefits high-quality preschool programs can have on children’s development. Confident in this knowledge, policymakers have expanded the availability of publicly funded preschool education programs. What is less well established, however, are the benefits children derive from programs of various durations and intensity. Preschool programs vary greatly—from less-than-half-day to full-day-plus programs. Little rigorous research is available to inform policy decisions about the relative benefits of programs with shorter and longer hours per day or days per year. To address this need, NIEER conducted a randomized trial in which 4-year-olds in a low-income urban district were randomly assigned to programs of different durations. The programs were otherwise quite similar: all had teachers with college degrees, a low ratio of children to teachers, and used the same curriculum."

Walters, C. (2014). Inputs in the production of early childhood human capital: Evidence from Head Start. (NBER Working Paper No. 20639). Cambridge, MA: National Bureau of Economic Research.

From the Abstract:
"Studies of small-scale "model" early-childhood programs show that high-quality preschool can have transformative effects on human capital and economic outcomes. Evidence on the Head Start program is more mixed. Inputs and practices vary widely across Head Start centers, however, and little is known about variation in effectiveness within Head Start. This paper uses data from a multi-site randomized evaluation to quantify and explain variation in effectiveness across Head Start childcare centers. I answer two questions: (1) How much do short-run effects vary across Head Start centers? and (2) To what extent do inputs, practices, and child characteristics explain this variation? To answer the first question, I use a selection model with random coefficients to quantify heterogeneity in Head Start effects, accounting for non-compliance with experimental assignments. Estimates of the model show that the cross-center standard deviation of cognitive effects is 0.18 test score standard deviations, which is larger than typical estimates of variation in teacher or school effectiveness. Next, I assess the role of observed inputs, practices and child characteristics in generating this variation, focusing on inputs commonly cited as central to the success of model programs. My results show that Head Start centers offering full-day service boost cognitive skills more than other centers, while Head Start centers offering frequent home visiting are especially effective at raising non-cognitive skills. Head Start is also more effective for children with less-educated mothers. Centers that draw more children from center-based preschool have smaller effects, suggesting that cross-center differences in effects may be partially due to differences in counterfactual preschool options. Other key inputs, including the High/Scope curriculum, teacher education, and class size, are not associated with increased effectiveness in Head Start. Together, observed inputs explain about one-third of the variation in Head Start effectiveness across experimental sites."

Wasik, B., & Snell, E. (2019). Synthesis of preschool dosage: How quantity, quality, and content impact child outcomes. In A. Reynolds & J. Temple (Eds.), Sustaining early childhood learning gains: Program, school, and family influences (pp. 31–51). Cambridge: Cambridge University Press. Retrieved from

From the Document:
"In recent years, increased attention has been paid to preschool as a means of addressing the significant achievement gap that exists between children in poverty and their more advantaged peers (Duncan & Murnane, 2011; Heckman, 2006; Yoshikawa, Weiland, Brooks-Gunn et al., 2013). However, preschool is expensive, and the nature of the debate has shifted from whether federal, state, and local monies should support early childhood learning to the specifics of for whom, how much, and what programs should offer. Therefore, understanding the amount, or dosage, of preschool needed to achieve positive outcomes in young children and to increase their school readiness is critical as policymakers and educators try to balance funding challenges while attempting to increase access to early education. However, the issue of dosage cannot be addressed independently from considerations about the content of the preschool classroom because the two factors are intricately related. In order to inform the discussion of how much preschool is effective, we need to understand how much of what is needed in order to unpack what the key components of an effective preschool experience are for young children."

Additional Organizations to Consult: National Institute for Early Education Research

From the Website:
"The National Institute for Early Education Research (NIEER) conducts academic research to inform policy supporting high-quality, early education for all young children and promoting the physical, cognitive, and social development needed for children to succeed in school and later life. NIEER provides independent, research-based analysis and technical assistance to policymakers, journalists, researchers, and educators."


Keywords and Search Strings: The following keywords, subject headings, and search strings were used to search reference databases and other sources: Preschool, Prekindergarten OR pre-k, Half-day OR part-day, Full-day

Databases and Resources: We searched ERIC for relevant resources. ERIC is a free online library of more than 1.6 million citations of education research sponsored by the Institute of Education Sciences (IES). Additionally, we searched Google Scholar and EBSCO databases (Academic Search Premier, Education Research Complete, and Professional Development Collection).

Reference Search and Selection Criteria

When we were searching and reviewing resources, we considered the following criteria:

Date of publications: This search and review included references and resources published in the last 10 years.

Search priorities of reference sources: Search priority was given to study reports, briefs, and other documents that are published and/or reviewed by IES and other federal or federally funded organizations, as well as academic databases, including ERIC, EBSCO databases, and Google Scholar.

Methodology: The following methodological priorities/considerations were given in the review and selection of the references:

  • Study types: randomized control trials, quasi experiments, surveys, descriptive data analyses, literature reviews, and policy briefs, generally in this order
  • Target population and samples: representativeness of the target population, sample size, and whether participants volunteered or were randomly selected
  • Study duration
  • Limitations and generalizability of the findings and conclusions

This memorandum is one in a series of quick-turnaround responses to specific questions posed by stakeholders in Alaska, Idaho, Montana, Oregon, and Washington, which is served by the Regional Educational Laboratory (REL) Northwest. It was prepared under Contract ED-IES-17-C-0009 by REL Northwest, administered by Education Northwest. The content does not necessarily reflect the views or policies of IES or the U.S. Department of Education, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.