As more young children enter school settings to attend early childhood programs, early childhood teachers and school psychologists have been charged with supporting a growing number of young children with chronic problem behaviors that put them at risk for the development of emotional/behavioral disorders (EBDs). There is a need for effective, feasible models that help school personnel address the needs of these young children within early childhood settings. This article describes Behavioral, Emotional, and Social Training: Competent Learners Achieving School Success (BEST in CLASS). BEST in CLASS is a classroom-based intervention designed to help early childhood teachers master effective instructional strategies for preventing and ameliorating problem behavior in young children at risk for EBDs through a teacher training and performance-based coaching model. The BEST in CLASS intervention model is described, and preliminary data are presented, followed by a discussion of implications for practice and future research directions.