Background: This longitudinal study examines the extent to which a school classroom (inclusive vs. special education) is meaningful for theory of mind (ToM) development among children with mild intellectual disability. Materials and Methods: The participant group consisted of 166 primary school-aged children (M = 8.1, SD = 0.99), 79 of whom attended inclusive classrooms; the remaining 87 were in special education classrooms. Results: Although all children developed ToM over time, children's learning of ToM in inclusive classrooms was significantly greater than that seen in special classrooms. The difference remained significant after controlling for age. The present authors have compared children's individual and family characteristics, but there were almost no differences between groups. Conclusions: The present authors discuss the results in the light of their importance for children's cognitive and social development. The implications for children's education are also considered.