Social-emotional competence is an important determinant of school readiness. School readiness, in turn, sets the stage for school success. There is clear longitudinal evidence that school success, attachment and bonding to the schooling process, and full engagement of schooling can, in combination, operate as a protective factor against a host of long-term health risk behaviors and negative outcomes. Herein, we describe an experimental study of an evidence-based model of early intervention. Head Start teachers and assistants in 13 centers participated in the study. Centers were randomly assigned either to a wait-list control condition or the intervention. This universal intervention was based, respectively, upon the emerging bodies of knowledge in Positive Behavior Support and Behavioral Coaching. The intervention program's application was associated with medium to large effect size improvements in participating students' overall social competence (as an essential school readiness skill) as measured through (a) enhancements in their ratings of adaptive student behavior and (b) corresponding decreases in student levels of challenging behavior and aggression as reflected on teacher rating scales. Feedback from participating teachers indicated they viewed their experiences with the intervention quite positively. (Contains 3 tables and 1 figure.)