The authors examined the initial and follow-up effect of Strong Kids, a social and emotional learning (SEL) curriculum, among a sample of 106 third- and fourth-grade students. Students were assigned to either the treatment or the wait-list condition and completed questionnaires on SEL knowledge and perceived use of SEL skills across 3 assessment periods (pretest, posttest, and follow-up). The classroom teachers also completed a social functioning questionnaire on each student at each assessment period. The classroom teachers implemented 12 weekly lessons from September to December, and 1 booster session in January. Generalization of SEL skills was promoted with verbal praise by treatment teachers to students outside of the lessons and by reminders to students to use the SEL skills they were learning. Fidelity of implementation was more than 85% and was measured by observing the number of components of the curriculum implemented. Analyses revealed that the treatment group had greater positive gains across all of the dependent measures from pre to posttest. These gains maintained at the 2-month follow-up period. The authors discuss the results in a schoolwide prevention framework and with implications for school psychologists. (Contains 4 tables and 4 figures.)