Minors are daily confronted with advertisements, which are occasionally controversial. In order to promote adolescents' moral advertising literacy, this intervention study explores how to stimulate secondary education students' knowledge on advertising law and their moral judgement of advertisements. Because a lot of new--especially online--advertising formats have arisen during the last years, 191 students from 12 classes were randomly assigned to either a no tablet condition or a tablet condition (to raise authenticity of learning material). The results show that students who use tablet devices perform less well on a post-test about advertising law. Regarding adolescents' moral judgement of advertisements, thematic analyses reveal that especially the use of nudity and feminine beauty are labelled as contentious in both conditions, because of, inter alia, the negative effects for adolescent girls' self-image and the desire to lose weight. After the intervention, the tablet condition has proven to be more effective in promoting critical thinking about nudity/feminine beauty in advertisements. However, none of the conditions did provide evidence that a critical attitude towards alcohol advertising is encouraged. In this regard, implications for future research in the context of advertising literacy education are discussed.