The first aim of this study was to evaluate the appropriateness of a short version of the Illinois Loneliness and Social Satisfaction Scale with children with special educational needs. The second aim was to explore loneliness in relation to self-perceived social integration, school well-being and the social self-concept of students from primary and secondary schools, in both inclusive and regular classes. This study had 1,115 student participants (408 fourth graders and 707 seventh graders), of whom 126 were diagnosed as having special educational needs. Factor analyses confirmed a unidimensional latent factor structure. The scale showed satisfactory reliability and the validity coefficients indicated that the scale is suitable for surveys including students with special educational needs. Generally speaking, the level of self-rated loneliness is low. Nevertheless, students with special educational needs in inclusive classes felt significantly lonelier than students without special educational needs in inclusive classes.