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<.001), indicating a negative relationship between an increase in the number of children per staff member on the process quality across publications. Additional moderator analyses showed that the correlation was higher for mixed–age classrooms and younger children and more relevant for global process quality indicators. Worse child-staff ratios correlated to a lesser degree with the interaction quality. Effect sizes also varied according to the type of staff included in the calculation of the child–staff ratio. These results underline that research evidence is rather heterogeneous and should not be interpreted without context. The authors discuss important implications for policy and pedagogical practice.