We present a variant of research-based learning in which teacher-training students in informatics courses were asked to participate in a Delphi process aimed at assessing the importance and difficulty of selected topics in lower secondary informatics education (grades 5 to 9). The analysis of the qualitative and quantitative data obtained during this process provides insights into when and how to address topics in lower secondary informatics education but also shows the effectiveness of the instrument with respect to the students´ competence development.