Summary.Detailed absence records are available for 3,273 primary school children from the National Survey of Health and Development. They are grouped in seven categories, according to the history of school attendances between 6 1/2 and 10 1/2 years. In the upper middle classes the eleven‐year mental ability and school performance test scores are unaffected by the amount of absence and by the age distribution of the absences. In all other social classes, considerable effects are recorded, children who are consistently absent or who are often absent in the last two years at primary school making low scores at eleven, and showing a relative deterioration in score between 8 and 11 years. On the whole, children who are often away in the first two years but make good attendances in the subsequent years catch up, but not if they come from the lower manual working class or go to primary schools that have a poor academic record. Even after allowing for the influence of absence on test performance, the children who are often absent get fewer grammar school places than expected; this is particularly noticeable for the manual working class childre