A meta-analysis published in Review of Educational Research summarises findings from studies that evaluated the effects of in-service training for early childhood teachers on the quality of early childhood education and care (ECEC) and child outcomes. Overall, data from 36 studies with 2,891 teachers was included in the analysis. For studies to qualify, child care quality had to be measured externally with certified raters at the classroom level.
The analysis, carried out by Franziska Egert and colleagues, revealed that at the teacher level, in-service training had a positive effect on the quality of ECEC, with an effect size of +0.68. Furthermore, a subset of nine studies (including 486 teachers and 4,504 children) that provided data on both quality ratings and child development were analysed, and they showed a small effect at the child level (effect size = + 0.14) and a medium effect at the corresponding classroom level (effect size = +0.45).
Source: Impact of In-Service Professional Development Programs for Early Childhood Teachers on Quality Ratings and Child Outcomes: A Meta-Analysis, Review of Educational Research, 88:3 401 – 433.