From the abstract: This article "reports on the results of a cluster randomized trial of the Incredible Years® Teacher Classroom Management Program (IY-TCM) and its effects on early elementary teachers' management strategies, classroom climate, and students' emotion regulation, attention, and academic competence. IY-TCM was implemented in 11 rural and semi-rural schools with K-2 teachers and a diverse student sample. Outcomes were compared for 45 teachers who participated in five full day training workshops and brief classroom consultation and 46 control teachers; these 91 teachers had a total of 1192 students. A high level of teacher satisfaction was found and specific aspects of the training considered most valuable for early elementary teachers were identified. Hierarchical linear modeling indicated a statistically significant intervention effect on Positive Climate in the classroom (d = 0.45) that did not sustain into the next school year. No main effects on student outcomes were observed, although a priori moderator analyses indicated that students with elevated social-behavioral difficulties benefitted with regard to prosocial behavior (d = 0.54) and inattention (d = − 0.34). Results highlight potential benefits and limitations of a universal teacher training program for elementary students, and suggest strategies for future delivery of the IY-TCM program and areas for future research."