This paper is based on a study of 7,372 students in grades 5-10 (aged 11-16) in a representative sample of Norwegian compulsory schools. The aim of the study was to examine the relationship between students' reported socio-economic status (SES) and their perceived social inclusion (SI) in school in the whole sample. We also considered separately a sub-sample of students with additional social background disadvantages, i.e. children taken into public care and placed in a foster home or children's home, those whose parents have alcohol- or drug-related problems, or students who are refugees and belonging to ethnic minority groups. For the sample as a whole, results showed a weak but significant relationship between SES and SI. In the disadvantaged sample, this relationship is stronger. These results suggest that additional social background disadvantages intensify the effects of SES on perceived social inclusion in school. (Contains 3 tables and 2 figures.)