There is growing evidence that social and emotional skills can be taught to students in school and teaching these skills can have a positive effect on later outcomes, such as better mental health and less drug use. This paper presents a benefit-cost analysis of a longitudinal social and emotional learning intervention in Sweden, using data for 663 students participating in the evaluation. Intervention costs are compared against treatment impact on self-reported drug use. Pre-test and post-test data are available. Since follow-up data for the participants´ drug use as adults is not available, informed projections have been made. Net present monetary values are calculated for the general public and society. The results show that students in the treatment group report decreasing use of drugs over the five year long intervention, the value of which easily outweighs the intervention costs.