Achievement and mental ability of physically late and early maturing schoolchildren related to their social background.

The results from achievement and mental ability testing in grades 3, 5, and 6 (ages 10, 12 and 13) of about 150 Swedish urban schoolchildren (boys and girls) were analysed according to the children's physical maturity (defined by late and early peak height velocity ages) and social background (defined by father's occupation). Social background played the main role in performance on both the achievement and most of the mental ability tests. Early maturers were, in general, superior to late maturers on the mental ability tests in grade 5. On verbally loaded tests and interaction between physical maturity and social background was found--early maturers scored higher than late maturers in the "lowest" social group, while a slight trend or no difference between early and late maturers was noticed for the 'upper' social groups.