A pre- and post-test quasi-experimental design was used to test the impact of a 30-week, theoretically-based social and emotional learning (SEL) curriculum, The RULER Feeling Words Curriculum ("RULER"), on the academic performance and social and emotional competence of 5th and 6th grade students (N = 273) in fifteen classrooms in three schools. Academic performance was assessed by report card grades. Social and emotional competence was assessed with teacher reports of student behavior. Students in classrooms integrating RULER had higher year-end grades and higher teacher ratings of social and emotional competence (e.g., leadership, social skills, and study skills) compared to students in the comparison group. This study provides preliminary empirical evidence that SEL programs like RULER improve important student outcomes. (Contains 4 tables.)