Background There has been considerable interest in the possible adverse neurocognitive effects of exposure to general anesthesia and surgery in early childhood.

Aims The aim of this data linkage study was to investigate developmental and school performance outcomes of children undergoing procedures requiring general anesthesia in early childhood.

Methods We included children born in New South Wales, Australia of 37+ weeks’ gestation without major congenital anomalies or neurodevelopmental disability with either a school entry developmental assessment in 2009, 2012, or Grade‐3 school test results in 2008‐2014. We compared children exposed to general anesthesia aged <48 months to those without any hospitalization. Children with only 1 hospitalization with general anesthesia and no other hospitalization were assessed separately. Outcomes included being classified developmentally high risk at school entry and scoring below national minimum standard in school numeracy and reading tests.

Results Of 211 978 children included, 82 156 had developmental assessment and 153 025 had school test results, with 12 848 (15.7%) and 25 032 (16.4%) exposed to general anesthesia, respectively. Children exposed to general anesthesia had 17%, 34%, and 23% increased odds of being developmentally high risk (adjusted odds ratio [aOR]: 1.17; 95% CI: 1.07‐1.29); or scoring below the national minimum standard in numeracy (aOR: 1.34; 95% CI: 1.21‐1.48) and reading (aOR: 1.23; 95% CI: 1.12‐1.36), respectively. Although the risk for being developmentally high risk and poor reading attenuated for children with only 1 hospitalization and exposure to general anesthesia, the association with poor numeracy results remained.