The dominant approach to children with disabilities is grounded in a biomedical model that assumes a direct relationship between the biological defect and the disability. From a cultural-historical point of view, this approach fails to notice how a child with a biological defect has to act in social institutions adapted to typical children. The aim of this article is to show how impairments arise from a developmental dynamic that includes both neurobiological and social conditions. Through empirical examples, the participation of children with severe disabilities is analyzed in relation to different practices and how they afford and develop particular cognitive activities, creating developmental possibilities or constraints that feed back on the child's learning. Distinguishing the different perspectives of children and professional adults increases our awareness of how conflicts between the participants' motives affect both participation and developmental conditions in practice. It is concluded that the learning problems of children with severe neurobiological impairments must be understood in terms of their social moderation and mediation. (Contains 1 table and 1 figure.)