Perhaps the two principal venues for the delivery of mental health services are schools and primary care practices. Unfortunately, these systems of care are poorly connected, which may result in care that is fragmented and suboptimal. This article describes the development and implementation of an electronic health record portal, known as the ADHD Care Assistant, to facilitate the sharing of information between schools and primary care offices to promote the use of evidence-based practices for managing children with behavioral health conditions. A feasibility study was conducted across 19 diverse primary care practices with 105 participating providers. Across the practices, 67% of providers activated the system for at least one patient and 32% activated it for five or more cases. Care Assistant use was lower in practices with a relatively high percentage of Medicaid patients (=25%). The article discusses challenges that have arisen among primary care providers, parents, and schools in using the Care Assistant, potential strategies for addressing the challenges, and directions for future research and practice.