Cohort, gender and spatial patterns of delayed school enrolment in third-grade children from 2009 to 2025

Delayed school enrolment can be an important marker for developmental delays and be associated with adverse health events. Analysing enrolment delays on an epidemiological level provides valuable insights in social, rural, socioeconomic or temporal variations. Using data from the EMOTIKON study, the influence of gender, rural and temporal variation was assessed on the frequency of children older than the key age (OTK) in a sample of 292,181 third-grade children in the Federal State of Brandenburg in Germany from 2009 to 2025. Temporal variation was analysed considering interference from significant events, specifically a change in regulation incorporating parental preferences and the onset of the SARS-CoV-2 pandemic. A generalised linear mixed model (GLMM) approach with a regression discontinuity design (RDD) revealed a substantial increase in the frequency of OTK children initiated by the change in regulation which persisted through the onset of the pandemic. The analysis further identified high regional socioeconomic deprivation, living far from metropolitan areas, living in midsize centres and being a boy as correlates of delayed school enrolment. These patterns suggests delays in school enrolment as a proxy for developmental delays to be heavily influenced by regulatory and social contexts, and at the same time highlights the importance of regional and gendered factors for school readiness assessments.