This study addresses the support provided by class staff in order to facilitate social participation of pupils with Down syndrome and peers in regular classes, and how they experience the interaction between the pupils. Data were collected through field observations of six pupils with Down syndrome in their class in mainstream schools, their six teachers and teachers' assistants. Qualitative interviews were conducted with the teachers and teachers' assistants. The analysis showed different support strategies, implying both environmental adaptations and individual support in order to facilitate peer interaction. A major finding was the role of the "supported ego", mainly provided by teachers' assistants. This role accommodated to the differences between the pupils, by compensating for the cognitive difficulties (i.e., perceptions, understanding and agency) of the pupils with Down syndrome. We concluded that class staff strived to keep the class as one unit by creating opportunities for participation for all the pupils through different strategies depending on their role and responsibility. (Contains 1 note.)