Middle schools are increasingly diverse places where students see and interact with peers different from themselves. However, students with and without intellectual disability (ID) have few opportunities to interact--they are together infrequently within extracurricular settings and the classroom. As such, students with ID are on the margins of the social fabric of the school, and middle schools are challenged to create a positive school experience for all students. This article focuses on how Special Olympics Unified Champion Schools (UCS) can advance developmental responsiveness and social equity in the middle grades through schoolwide social inclusion of students with ID. Data from a multi-year national evaluation provides evidence that UCS can support middle schools to create a positive school experience for all students that aligns with Association for Middle Level Education's essential attributes of education for young adolescents (i.e., responsive, challenging, empowering, equitable, engaging), addresses the developmental and social needs and interests of young adolescents, and meets benchmarks for high-performing schools set forth by the National Forum to Accelerate Middle-Grades Reform's Schools to Watch (STW) Program®. STW Program criteria establish a framework for schools to commit to an environment that prioritizes what is best for the developing adolescent, including adolescents with ID.