This study addresses the convergent validity of a new teacher questionnaire to assess the social participation of students with special needs in regular primary schools. The Social Participation Questionnaire (SPQ) consists of four subscales representing four key themes of social participation: friendships/relationships, contacts/interactions, student's social self-perception, and acceptance by classmates. The study took place in Grades 1 to 3 of regular Dutch primary schools that had at least one student with an official special-needs statement. A confirmatory factor analysis using the LISREL program provided evidence for the SPQ's convergent validity. The outcomes support the model of social participation distinguishing four key themes. The fit indexes suggest that our model is theoretically viable for Grades 1 and 2 but only partly viable for Grade 3. (Contains 1 figure, 7 tables, and 1 note.)