The role of teacher behavior management for children's disruptive behavior development (hyperactive and oppositional behavior) was investigated using a universal classroom preventive intervention study. Five-hundred seventy children were followed from second to third grade of elementary school. Observations of teacher behavior management and children's on-task and off-task classroom behavior and peer reports of hyperactive and oppositional behavior were available. Results showed that the reduced use of negative remarks of intervention teachers predicted children's increase in on-task behavior and decrease in talking-out behavior. These improved children's classroom behaviors in turn mediated the impact of the intervention on the development of hyperactive and oppositional behavior over the studied period. These results were similar for girls and boys. The results underscore the role of teachers' classroom management strategies in improving children's classroom behavior, which, in turn is an important component in the reduction of disruptive behavior development.