Using Norwegian data, we examine effects of school starting age (SSA). Unlike much recent literature, we can separate SSA from test age effects using scores from IQ tests taken outside school at about age 18. We find a small, negative effect of starting school older but much larger positive effects of age at test. Also, starting older leads to lower earnings until about age 30. We find little impact of SSA on educational attainment, but boys who start older are less likely to have poor mental health at age 18. Additionally, starting school older has a negative effect on the probability of teenage pregnancy.

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