Intelligence tests have made a large contribution to the analysis of the capacity of pupils to do school work. There is a marked correlation between the scores made by pupils on intelligence tests and the achievements of these pupils in their courses. The correlation is far from perfect, however, and there is clear evidence that the lack of closer correlation is due not simply to errors in the measurement of intelligence and of achievement but to the presence in achievement of factors other than intelligence. Attempts to explain the discrepancy between intelligence and achievement in individual cases frequently produce convincing evidence that the discrepancy is due to some characteristic of the individual other than intellectual