A description of the Behavioral, Emotional, and Social Training: Competent Learners Achieving School Success (BEST in CLASS) classroom-based intervention designed to help early childhood teachers master instructional strategies for preventing and ameliorating problem behavior in at risk young children, and a pilot study to examine teachers' ability to implement the program as well as its influence on children's problem behaviors, social competence, and teacher-child relationships, based on data from 10 early childhood teachers and 19 3- to 5-year-old children