There are few tools to assess the effectiveness of climate change education in non-formal context. Moreover, they often lack solid theoretical foundations. In the context of the Sors de ta bulle campaign led by the Fondation Monique-Fitz-Back, an innovative evaluation framework based on twelve indicators was developed. These indicators were used to assess the impacts of the participation of high school students in the Youth Climate Change Summit, one of the campaign activities. A mixed-methods design combining an online survey and a group interview showed that the impacts on participants were threefold : increasing motivation, strengthening of perceived personal efficacy and intensification of the engagement in the fight against climate change.