Selection effects in the Swedish Scholastic Aptitude Test due to socioeconomic status (SES) were studied using data from longitudinal studies (n=8,222). Results show that subjects from low SES groups constitute the most positively-selected group even though they obtain the lowest test scores. Gender and grade differences are discussed. (MAK)

A summary and discussion of a series of studies considered the dilemma that equal educational treatment of all children in public schools appears likely to increase the spread of differences among them in educational achievement. Longitudinal studies of pairs of identical and of fraternal twins in Sweden from 10 to 18 years of age considered the…