Although primary care practices and schools are major venues for the delivery of mental health services to children, these systems are disconnected, contributing to fragmentation in service delivery. This paper describes barriers to collaboration across the primary care and school systems, including administrative and fiscal pressures, conceptual and linguistic differences between health care and educational professionals, role restrictions among professionals, and privacy laws. Strategies for overcoming these barriers, which can be applied in both primary care and school settings, are described in this paper. This paper has a primary focus on children with attention-deficit/hyperactivity disorder, but the principles and strategies described are applicable to children with a range of mental health and health conditions.