Background: This study aimed at assessing the impact of including children with intellectual disability (ID) in general education classrooms with support on the academic achievement of their low-, average-, and high-achieving peers without disability. Method: A quasi-experimental study was conducted with an experimental group of 202 pupils from classrooms with an included child with mild or moderate ID, and a control group of 202 pupils from classrooms with no included children with special educational needs (matched pairs sample). The progress of these 2 groups in their academic achievement was compared over a period of 1 school year. Results: No significant difference was found in the progress of the low-, average-, or high-achieving pupils from classrooms with or without inclusion. Conclusions: The results suggest that including children with ID in primary general education classrooms with support does not have a negative impact on the progress of pupils without disability. (Contains 2 tables.)