This study examined how training, dosage, and implementation quality of a social and emotional learning program, The RULER Approach, were related to students' social and emotional competencies. There were no main effects for any of the variables on student outcomes, but students had more positive outcomes when their teachers (a) attended more trainings and taught more lessons, and (b) were classified as either moderate- or high-quality program implementers. Student outcomes were more negative when their teachers were classified as low-quality implementers who also attended more trainings and taught more lessons. Post hoc analyses revealed that low-quality implementers felt less efficacious about their overall teaching than high-quality implementers. The discussion focuses on the importance of assessing the interaction of training and implementation variables when examining the effect of social and emotional learning programs. (Contains 3 tables.)