The literature dealing with the inclusion of children with autism spectrum disorder (ASD) in mainstream schools has increased over recent years, propelled by the argument that it will improve the quality of life, educational performance and social development of included children. This area of research is currently an important one for the development of policy and practice. The literature on inclusion dealing with the inclusion of children with ASD is limited, so the implementation of inclusion has preceded research. The current study investigated whether children in mainstream placements show enhanced performance, relative to those in specialist provisions. The study used a combination of primary and secondary data analysis to explore the impact of inclusion on children with ASD in four authorities in the south east of England. The results suggest that mainstream children have no greater academic success than children in specialist provision. The study suggests that a number of specific provisions are involved in promoting success, such as Speech and Language Therapy, and the impact of Learning Support Assistants, and these are also reviewed and discussed.