Children with special needs who are pupils in a mainstream classroom need not only individual support, but also classwide support. The purpose of the present study was to clarify how a child needing special support interacted with the other children in his class during lessons. The method used was participant observation, with a focus on classroom discourse. The observations were analyzed from the standpoint of Vygotsky's defectology. In that method of analysis, the problem-solving process used by children with disabilities is significant. In a process called <i>detour</i>, a child with a disability uses different tools to solve problems, compared to children without disabilities. Interactions of a child with special needs and the other children in that pupil's class should be examined, because <i>detour</i> is considered to influence the surrounding children. The following observations were made: (a) Even though the child with a disability had previously had poor communication skills, with <i>detour</i>, he was able to interact effectively with others. (b) The child for whom support was necessary also influenced the other children and transformed their actions. Thus, it is important to examine further the supports that classroom teachers provide for children with special needs. If teachers understand how children with special needs function in a classroom environment and how they interact with other children, they can enhance the special support provided by using classroom discourse more effectively.