The question of differentiation in school systems have been discussed for long time, all over the world. There are external and internal ways of differentiate education. Ability grouping is reported the most common way of internal differentiation between students and groups of students, although global research for the past decades shows that the effects of ability grouping are mostly negative, for all kinds of students, with some few exceptions.
Focus for the study is the extent of ability grouping and in which subjects it is used, in all Swedish upper secondary schools. This has not been investigated at a national level before, and the gap of research in the field is pointed out in previous research.
The data used is collected by a questionnaire of all schools (N=950), with a response rate of 80.4%. Results show that (1) it is frequent with ability grouping, about 43% of the schools report using it in some way. (2) It is most frequent to use it in the foundation subjects, and especially in mathematics. (3) The analysis also shows that there are no differences in the use of ability grouping between types of schools (independent- and public schools), or between schools located in different parts of the country. (4) It is also shown that small schools use ability grouping to a greater extent than large schools do.
The frequent extent of ability grouping in the Swedish upper secondary schools is critically discussed in relation to previous research, which indicates negative effects.