The relationship between the child–staff ratio and process quality in early childhood education institutions: A meta–analysis

• There was a small negative correlation between higher child-staff ratios and lower process quality. • Results on the association of child-staff ratios and process quality were heterogeneous. • There was a small to medium negative correlation in mixed-age classrooms and for children ages 0-2. • There was a small negative correlation for global process quality and a very small negative correlation for interaction quality. • There was a small negative correlation for the child-staff ratio, including only ECEC professionals. This meta–analysis studies the association between the child–staff ratio and the process quality (ERS, CLASS, CIS, ORCE, and EQOS) in center–based Early Childhood Education and Care (ECEC) institutions and identifies potential moderating factors. It synthesizes evidence from 49 publications from 14 countries with data from 18.049 ECEC classrooms. Results of the three–level random effects model provided a small significant negative correlation (Z = – 0.12, p