Citizen science has the potential to promote an understanding of science and to represent science in school authentically. Still, its implementation into formal education encounters tensions between scientific and educational goals. Factors for success and hindrances of the implementation of citizen science projects in the classroom can be described using a supply-use-outcome model. We carried out a scoping review on the implementation of such projects in secondary school lessons and mapped n = 60 selected articles (out of N = 2.105) in the supply-use-outcome model. A total of 65 success and hindering factors were reported in the articles, with the success factors predominating. Most of the success and hindering factors consistently point to the design of the citizen science project and the prerequisites of the teachers, scientists and intermediaries. In practice, it should be more clearly outlined how the projects contribute to curricular objectives for implementation in the classroom and the competencies of the stakeholders mentioned should be expanded. Future research should increasingly report on hindering factors so that these can be better addressed.