Diminishing civic vitality has been reported in numerous societies, irrespective of democratic maturity. Mandatory community service initiatives in schools have garnered attention as a strategy for fostering long-term civic engagement. However, methodological challenges such as selection bias and observation timing have led to inconsistent empirical results. This study leverages a unique natural experimental context where mandatory community service requirements were nationally implemented in middle and high schools in South Korea. Employing a non-parametric regression-discontinuity design, we provide robust evidence that such programs increase the likelihood of volunteering in adulthood among lower socioeconomic groups. We found no indications that these mandates increase or decrease the propensity for civic engagement among higher socioeconomic groups. [This paper was published in "VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations" v36 n1 2025.]