Objectives The effectiveness of early childhood education and care (ECEC) programs for children's development in various domains is well documented. Adding to existing meta-analyses on associations between the quality of ECEC services and children's developmental outcomes, the present meta-analysis synthesizes the global literature on structural characteristics and indicators of process quality to test direct and moderated effects of ECEC quality on children's outcomes across a range of domains. Design A systematic review of the literature published over a 10-year period, between January 2010 and June 2020 was conducted, using the databases PsychInfo, Eric, EbscoHost, and Pubmed. In addition, a call for unpublished research or research published in the grey literature was sent out through the authors' professional network. The search yielded 8,932 articles. After removing duplicates, 4,880 unique articles were identified. To select articles for inclusion, it was determined whether studies met eligibility criteria: (1) study assessed indicators of quality in center-based ECEC programs catering to children ages 0-6 years; and (2) study assessed child outcomes. Inclusion criteria were: (1) a copy of the full article was available in English; (2) article reported effect size measure of at least one quality indicatorchild outcome association; and (3) measures of ECEC quality and child outcomes were collected within the same school year. A total of 1,044 effect sizes reported from 185 articles were included. Results The averaged effects, pooled within each of the child outcomes suggest that higher levels of ECEC quality were significantly related to higher levels of academic outcomes (literacy, n = 99: 0.08, 95% C.I. 0.02, 0.13; math, n = 56: 0.07, 95% C.I. 0.03, 0.10), behavioral skills (n = 64: 0.12, 95% C.I. 0.07, 0.17), social competence (n = 58: 0.13, 95% C.I. 0.07, 0.19), and motor skills (n = 2: 0.09, 95% C.I. 0.04, 0.13), and lower levels of behavioral (n = 60: -0.12, 95% C.I. -0.19, -0.05) and social-emotional problems (n = 26: -0.09, 95% C.I. -0.15, -0.03). When a global assessment of child outcomes was reported, the association with ECEC quality was not significant (n = 13: 0.02, 95% C.I. -0.07, 0.11). Overall, effect sizes were small. When structural and process quality indicators were tested separately, structural characteristics alone did not significantly relate to child outcomes whereas associations between process quality indicators and most child outcomes were significant, albeit small. A comparison of the indicators, however, did not yield significant differences in effect sizes for most child outcomes. Results did not provide evidence for moderated associations. We also did not find evidence that ECEC quality-child outcome associations differed by ethnic minority or socioeconomic family background. Conclusions Despite the attempt to provide a synthesis of the global literature on ECEC quality-child outcome associations, the majority of studies included samples from the U.S. In addition, studies with large samples were also predominately from the U.S. Together, the results might have been biased towards patterns prevalent in the U.S. that might not apply to other, nonU.S. ECEC contexts. The findings align with previous meta-analyses, suggesting that ECEC quality plays an important role for children's development during the early childhood years. Implications for research and ECEC policy are discussed.
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