Effects of a packaged teacher-consultant-mediated intervention program (CLASS) for modifying acting-out behavior in the regular classroom were evaluated in two experiments. Consultants were instructed (a) as part of an 8-week course by two briefly trained college instructors or (b) in a 2-4-day workshop by the program's developers. Fifty-four primary-grade experimental and control children from three school districts were involved. The results indicated the experimentals, in contrast to the controls, significantly increased their proportion of appropriate behavior postintervention and in the next academic year (Experiment 2) and required fewer remedial services and special class placement up to 3 years later. The program's external generalizability and cost-effective service-delivery strategy are discussed.