<p>This study investigated whether attending mainstream school is associated with improved social inclusion among children on the autism spectrum and their parents. The cross-sectional study took place from July to August 2023 at 30 rehabilitation centers for children on the autism spectrum in Hunan Province, China. Participants included 860 children aged 3–14 years, with autism history receiving outpatient rehabilitation services, and their primary caregiver parents aged 23–54 years. Social inclusion among children on the autism spectrum was evaluated using the Chinese version of the social inclusion subscale of the KidsLife-ASD Scale. Parental social inclusion was assessed using the Chinese version of the Social Inclusion Scale. Linear mixed models were used to explore the association between attending mainstream school and social inclusion. Among children on the autism spectrum, 36.2% attended mainstream school. These children showed significantly higher levels of social inclusion compared to non-attenders. Subgroup analysis based on the severity of autism symptoms revealed that the significant association remained in both the mild and moderate/severe subgroups, being more pronouced in the mild subgroup (<i>P</i>_{for interaction}&#xa0;&lt;&#xa0;0.001). Parents of children attending mainstream school reported greater social inclusion levels than those whose children did not; however, after adjusting for severity of autism symptoms and other factors, this association became non-significant. Our study demonstrates a positive association between attending mainstream school and social inclusion for children on the autism spectrum, highlighting the critical role of mainstream school education in fostering social opportunities and providing diverse learning resources. It also underscores the need for targeted support strategies for parents.</p>