A cohort of students was monitored throughout their nine-year comprehensive school career to investigate social segregation in Swedish schools. The study began in the school year 1972-73 and the students came from six large municipalities: Stockholm, Botkyrka, Lidingo, Malmo, Linkoping, and Boras. It found that, despite reforms allowing all pupils, regardless of their social class, to attend the same type of school, differences in educational results continue to reflect social status. Student performance in class and on standardized tests differed according to status and, when making choices for senior level grades, higher social class students tended to choose a more academic combination of subjects. These differences are governed by the students' social identity, which they acquire as a result of social segregation in school and elsewhere. School segregation may simply be based on residential segregation. But even the student welfare institution, intended to deal with problems not addressed within educational activities, is overtly discriminatory. It was found, for example, that low achievers in high status classes obtained more support than the corresponding students in low status classes. Practices of the pupil welfare institution result in referring problems to individual differences between students, and not to the discriminatory treatment which schools apparently accord to students of different social classes. (KH)