Taiyo Fukai

Abstract There is a pressing need for professional development (PD) programs in early childhood education and care (ECEC) that address teachers’ challenges and enhance ECEC quality. This study evaluated the effectiveness of a brief, efficient PD program using a cluster randomized controlled trial in Japan. Twenty classes ( N  = 20) of 5-year-olds from three kindergartens and 14 accredited childcare centers in a single city in the Tokyo metropolitan area were randomly assigned to treatment or control groups. ECEC quality was assessed at baseline and endline using the Early Childhood Environment Rating Scale, 3rd edition (ECERS-3). Teachers and center directors in the treatment group received an approximately 1-hour online intervention with a coaching style from an expert, targeting ECERS-3 items that scored below three at baseline. The program significantly improved ECEC quality, producing a 0.88 standard deviation increase in the ECERS-3 total score (Hedges’ g = 0.93). Improvements were observed in three domains: “Teacher’s attitude,” “Object-related,” and “Time use.” This study confirms the effectiveness of a time-efficient PD program for enhancing ECEC quality. The findings provide practical insights for implementing PD programs in non-Western contexts and demonstrate the potential of scalable PD models in diverse international settings.