Currently, more than two thirds of school-aged children with mental health needs do not receive treatment. By exploring the numerous barriers that limit children's access to mental health care, the authors argue that school psychologists have a key role to play in supporting comprehensive mental health services for children. This article provides a rationale for collaboration between medical and school professionals in order to best address children's mental health needs. Various social and economic barriers limit children and adolescents' access to specialized mental health services. Still other barriers, including state legislation and time constraints, influence the degree to which school psychologists are able to engage in mental health service provision and collaboration. While recognizing these obstacles, a model of collaborative service provision that closes the gap between current and best practices of mental health service provision in the schools is proposed. (Contains 1 figure.)