The Peace Program is a school-based social emotional learning program. Despite increased efforts to develop, implement, and evaluate school-based SEL programs in the past few decades, the short- and long-term effectiveness of such programs remains unclear. Considering the previously identified gaps that may contribute to modest effect sizes and erosion of initial effects over time, we conducted a feasibility study to better understand adoption and implementation of a local SEL program in order to inform future program design, delivery, and evaluation. Using mixed-methods, feasibility indicators: program acceptability, facilitator competence, and students’ social–emotional outcomes were examined. Qualitative data were analyzed using thematic analysis. Outcome analyses were conducted on facilitator competence measures and student outcomes using mixed-model repeated measures analysis of variance. Qualitative results indicated acceptance for the Peace Program. Facilitators demonstrated competence, with no difference across grade, classroom, or schools. Significant interactions effects were found for students’ aggression, concentration/attention, and emotional competence. School-level associations were found for students’ concentration/attention. Implications of results and future directions are discussed, including the critical role of teachers and social workers in promoting SEL among socioeconomically disadvantaged children; the impact on SEL programming on children in early elementary grades; and the potential effects of school climate and culture.