Despite research demonstrating the importance of student-teacher relationships for student functioning, little is known about strategies to enhance such relationships, particularly in secondary school. The current study examined effects of a professional development for middle school teachers on the Establish-Maintain-Restore (EMR) approach. EMR aims to enhance teachers' skills in cultivating relationships with students and involves brief training (3 hr) and ongoing implementation supports. In a randomized controlled trial, 20 teachers and 190 students were assigned to EMR or control. Observers rated academically engaged time and disruptive behavior, and teachers reported on relationship quality. Multilevel models showed that EMR resulted in significant improvements in student-teacher relationships (Hedge's g = .61, 95% CI 0.21, 1.02), academically engaged time (g = .81, 95% CI 0.01, 1.63), and disruptive behavior (g = 1.07, 95% CI 0.01, 2.16). Results indicate potential promise for EMR. Impact and Implications This study tested a novel, brief training for middle school teachers aimed at enhancing their skills in building relationships with students, called Establish-Maintain-Restore (EMR). Students of EMR-trained teachers had improved behavior in the classroom. While these findings suggest that EMR is a promising cost-effective strategy for improving student behavior, more research is needed to test its impact on student achievement.