Early Childhood Education and Care and Developmental Vulnerability at School Entry.

Importance: Early childhood education and care (ECEC) is widely recognized for supporting children's development and school readiness; however, evidence from Western Australia remains limited. Objective: To examine the association between ECEC attendance and developmental vulnerability at school entry. Design, Setting, and Participants: This population-based cohort study included children participating in Australian Early Development Census waves in Western Australia from 2009 to 2021. Analyses were conducted between November 2025 and January 2026. Exposure: The primary exposure was participation in ECEC, defined as attendance at either preschool or daycare before starting full-time school. Preschool and daycare were also examined separately. Additional analyses examined overlapping ECEC exposure patterns, including children who attended both preschool and daycare. Main Outcomes and Measures: Developmental vulnerability on 1 or more domains (DV1) and on 2 or more domains (DV2) across 5 Australian Early Development Census domains: physical health and well-being, social competence, emotional maturity, language and cognitive skills (school-based), and communication skills and general knowledge. Mixed-effects modified Poisson regression with robust SEs estimated adjusted relative risks (aRRs). Results: Of 123 256 children, complete data were available for 117 691 children in the ECEC analysis (59 335 [50.4%] male; 87 216 [74.1%] aged 5 years 1 month to 5 years 10 months), 117 496 in the preschool analysis (59 234 [50.4%] male; 87 089 [74.1%] aged 5 years 1 month to 5 years 10 months), and 85 544 in the daycare analysis (43 289 [50.6%] male; 63 155 [73.8%] aged 5 years 1 month to 5 years 10 months). Preschool attendance was high (95.0%; 111 650 children), whereas daycare attendance increased from 23.1% (4362 children) in 2009 to 37.1% (6478 children) in 2021. ECEC attendance was associated with a reduced risk of developmental vulnerability (DV1, aRR, 0.78; 95% CI, 0.74-0.82; DV2, aRR, 0.67; 95% CI, 0.62-0.72). Similar associations were observed for preschool. In contrast, daycare attendance was associated with a higher risk of DV1 (aRR, 1.09; 95% CI, 1.06-1.13) and DV2 (aRR, 1.15; 95% CI, 1.10-1.21), with higher vulnerability in social competence and emotional maturity but lower vulnerability in language and cognitive skills (school-based) and communication skills and general knowledge. Conclusions and Relevance: In this cohort study of 123 256 children, participation in ECEC, particularly preschool, was associated with lower developmental vulnerability at school entry. These findings support efforts to improve equitable access to early childhood education. The heterogeneous associations for daycare attendance suggest that differences in participation patterns, timing, and contextual factors may influence developmental outcomes and warrant further investigation.