Scores on ability tests given to 1,274 students in grades 4-6 and 1,310 in grades 7-9 were simultaneously factor analyzed at class and individual levels. At the individual level, the general factor was most highly loaded on fluid abilities. Three common factors were established at the class level. (SLD)

A comparison was made of ability and achievement test results and school grades for 323 pairs of Swedish male and female twins and 740 controls in relation to social background. An interaction effect of sex and social background was found for verbal ability and mathematics test results. (SLD)