This paper describes Extended Day Treatment (EDT), an innovative intermediate-level service for children and adolescents with serious emotional and behavioral disorders, delivered in the after school hours. The current paper describes the core components of the EDT model of care within the context of statewide systems of care, including its theoretical foundations, core service components, relation to evidence-based practices, workforce composition and staff training, and data collection and reporting mechanisms. Recommendations are provided for statewide implementation, followed by discussion of model development as an approach to systems reform for the treatment of children and youth with emotional and behavioral disorders.