For many years empirical studies have repeatedly pointed to the need to improve the economic competence of adolescent and young adults. This demand is already reflected -- at least in part -- in the inclusion of economic content in the curriculum of general educational schools. However, the curricular implementation seems to be only partially comprehensive enough to sufficiently support the acquisition of economic competence, so that non-formal and informal learning opportunities do not lose their importance as a supplement to the general curriculum-based framework. The research situation, however, is hardly given with regard to empirical findings on the effectiveness of such learning opportunities for the acquisition of economic competence. Therefore, our intervention study examines the role of non-formal learning opportunities in the economic field as a supplement to normal economic teaching lessons and how these learning opportunities affect the competence development of students in general educational schools. The results show that the intervention group was able to improve its economic competence significantly more than the control group. Furthermore, it becomes clear that over the intervention period the influence of personal factors loses relevance for the prediction of economic competence, but only for the intervention group.