We examined whether relations between classroom composition and individual school achievement, academic self-concept, and interest are comparable in magnitude between special education schools and regular schools. Analyses were based on data from the IQB Trends in Student Achievement 2016, a nationally representative large-scale assessment of German fourth-graders. The sample consisted of 1,249 students with special educational needs in the area of learning disabilities, speech and language impairment, and emotional disorders (SEN-LSE) from 157 classrooms in special education schools and 998 students with SEN-LSE as well 11,029 classmates without SEN-LSE from 568 classrooms in regular schools. In both school types, class-average cognitive abilities were positively related to individual achievement, whereas class-average achievement was negatively related to students’ academic self-concept. Effects of class-average achievement on students’ interest differed in magnitude between special education schools and regular schools. Results suggest that, overall, established composition effects can be generalized to students with SEN-LSE in both school types.