Prior research on COVID-related school disruptions focused mainly on primary or secondary, with limited studies on kindergarten children. Using a naturalistic quasi-experimental design, we examined whether school disruption during the first year of kindergarten (K1) affected early numeracy, literacy, and non-academic development. We also examined whether disruption during the first or second year of kindergarten (K2) was more detrimental to children's development. A cohort of K2 students from each of two consecutive years (N = 235, 4–5-year-old) were recruited from ten kindergartens in Hong Kong, which had long periods of COVID-related school disruptions. One cohort was assessed just before the onset of COVID-19; the other, one year later. K1 disruption did not affect performance at K2. In contrast, performance at K3 showed that K2 disruption had a more detrimental effect on physical performance than K1 disruption. Findings highlight the period and aspects of children's development that are particularly sensitive to schooling. Copyright © 2025 Informa UK Limited, trading as Taylor & Francis Group.