[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The purpose this study was to examine the treatment effects of an evidence-based teacher training -- Incredible Years Teacher Classroom Management (IY TCM) -- for children with aggression. Specifically, treatment effects were expected to be demonstrated on both academic achievement and behavioral performance. Previous studies have accumulated evidence regarding the co-occurrence of children's aggressive behavior and academic failure (Darney et al., 2012; Reinke et al., 2008); the negative trajectories continue for them, indicating negative outcomes in adolescent and adulthood. When children enter school, they spend more time learning with peers and being supervised by school teachers. Classroom management has been demonstrated as a factor in either escalating children's aggressive behavior or decreasing those problematic behaviors (Reinke and Herman, 2002; Webster-Stratton et al., 2001). IY TCM trains teachers in evidence-based practices of effective practical behavioral management strategies, teacher-child relationship skills, parent-teacher collaboration, behavior plans addressing developmentally appropriate goals for individual students, and ways to promote students' emotional regulation, social skills and problem-solving skills. Previous studies about IY TCM were mostly conducted with other treatments of IY series. This study was one of the first studies to investigate treatment effectiveness of IY TCM. Participants included 1818 students (Grade K to 3) and 105 teachers from nine elementary schools in a large Midwestern school district. 52 teachers were randomly assigned to receive IY TCM, indicating 901 students in the intervention group. 74 % of the participated students are African American and 50 % of them received free reduced lunch (FRL). All outcome variables were assessed before and after intervention implementation. Results support the hypotheses associated with research questions one and two which indicated that higher levels of aggression as reported by teachers would be associated with lower academic achievement on both reading and math at the beginning of school year and the end of school year controlling demographic variables such as gender, FRL and race. A hierarchical linear regression analysis was conducted to examine the main effects and the hypotheses that baseline levels of aggression moderate the relationship between intervention status and outcomes. Results indicated a significant intervention status by baseline aggression interaction moderated children's math achievement. Additionally, significant moderation was found on children's emotional regulation and prosocial behaviors. Lastly, research question five and six focused on evaluating whether students with high level of aggressive behavior would demonstrate greater growth in academics and social emotional performance in comparison to less aggressive children in the treatment group. The hypothesis of greater improvement on academic achievement or social emotional performance for children with higher levels of aggression than their classroom peers post intervention was not supported. Further implication for practice and direction for future research based on the findings were discussed.