The present study investigated how the educational placement in special education schools or regular schools is related to the achievement motivation of students with special educational needs (SEN). Furthermore, we examined whether the classroom social environment (i.e., class-average achievement and social support) explains potential placement differences. We compared the academic self-concept and enjoyment of learning of SEN students in special education schools (n = 420) and regular schools (n = 678) at the end of 4th grade. In line with social comparison theory, SEN students in special education schools reported higher academic self-concepts and enjoyment of learning than their peers in regular schools. Examining underlying mechanisms, class-average achievement was negatively related to SEN students’ academic self-concept and enjoyment of learning. In contrast, individually perceived social support by classmates—but not class-average social support—was positively associated with SEN students’ achievement motivation. After controlling for individual and class-average achievement, no relationship between SEN students’ educational placement and achievement motivation was found. Results indicate that social comparisons with classmates may result in placement differences in SEN students' academic self-concept and enjoyment of learning.