Vaginal instrumental delivery is a common obstetrical intervention, but its effect on children's later development is not well known.To determine if vaginal instrumental delivery is associated with adverse neurodevelopment as measured by school achievement.We performed a whole-of-population study involving linkage of routinely collected perinatal data with school assessments among children born in South Australia from 1999 to 2008. Participants were singleton children born by forceps (n = 5494), ventouse (n = 6988), or normal delivery (n = 80 803). School achievement was measured through performance on the National Assessment Program in Literacy and Numeracy (NAPLAN), at around eight years of age. This assessment involved five domains and scores were categorised according to performing at or above National Minimum Standards (NMS). Effects of instrumental versus normal vaginal delivery were analysed via augmented inverse probability weighting (AIPW), taking into account a variety of maternal, perinatal and sociodemographic characteristics.In unadjusted analyses, instrumental delivery was not associated with poor NAPLAN scores. AIPW analyses also suggested that instrumental delivery had minimal adverse effect on NAPLAN scores, with the largest difference being lower spelling scores among forceps-delivered children (-0.022 (95% CI -0.0053-0.009)) compared with spontaneous vaginal births. The findings were consistent among exploratory subgroup analyses involving births in the absence of prolonged labour, with APGAR ≥ 9, and among normotensive and non-diabetic mothers.In singleton children born at term, instrumental delivery does not have an adverse effect on neurodevelopment as measured by NAPLAN performance at age eight.