Extended day treatment (EDT) is an innovative intermediate-level service for children and adolescents with serious emotional and behavioral disorders delivered during the after school hours. This paper describes the core components of the EDT model of care within the context of statewide systems of care, including its core service components, levels of care, focus on 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 treating children and youth with emotional and behavioral disorders.