The aim of this study was to find out about attitudes toward inclusion and benefits perceived by families with children enrolled in schools attended by students with ASD at different educational stages (from kindergarten to high school). 323 families of classmates of students with ASD from different educational stages of 16 mainstream schools participated. The analysis of the attitudes, perceived benefits, relationship with the teacher, and relationship with the school was carried out through questionnaires. The results show positive attitudes toward the inclusive education of students with ASD in all families, but especially among families of children with SEN. All the families identified the benefit of inclusion. Attitudes are related to collaboration with the school and satisfaction with teachers.