Despite its importance in social development, social understanding has hardly been studied in high-ability children. This study explores differences in social understanding between children in high-ability and regular classrooms, specifically theory of mind (ToM) and perception accuracy, as well as associations between individual characteristics (age, gender, peer acceptance, and cognitive ability) and social understanding. Participants were 671 children in Grades 1 to 6 (55% boys; M age 9.20 years). Children in high-ability classrooms had higher ToM scores in Grades 1 to 3 and were more accurate perceivers of acceptance than children in regular classrooms. No group differences were found for ToM in Grades 4 to 6. ToM was associated with several individual characteristics, in particular age and cognitive ability. Perception accuracy was mainly related to peer acceptance. Suggestions for future research and implications for practitioners are discussed.