Summary.Continuing a previous study, the proportion of children in a representative sample of 1200 15‐ to 16‐ year‐olds showing different Piagetian levels of thinking was measured. No increase in the proportion showing formal operational thinking was found beyond the age of 15. On the three tests used a retrospective analysis of both surveys for sex differential showed no increase for girls after 14, while the boys continued for a further year. The pendulum problem showed no sex differential, and the boys indicated level was, on average, the same on all three tests. The girls' performance was substantially lower on the test on spatial relationships, and on the test on volume and density, throughout the age‐range