We report on the results of a randomised controlled trial conducted among over 2,000 children in 60 elementary schools in rural Shaanxi Province, North-west China. We find that providing children with daily iron supplements for six months improved children’s haemoglobin levels and standardised maths scores. In comparison, educating parents about nutrition and anaemia in a special parents meeting produced a modest impact on children’s haemoglobin levels. We also find heterogeneous intervention effects by children’s gender, anaemia status and boarding status. Overall, iron supplementation is more effective. However, given its low cost and simple implementation, parental education should still be considered.