The implementation of educating "Basic Life Support (BLS) competences" in German schools is particularly affected by the often reported "implementational gap" --limited transfer of empirical findings into practice. This Design-Based Research (DBR) study evaluates two different methodologies for BLS teaching, generating implications for transfer. Students (N = 136) of a secondary school (11-13 years) were assigned to different methodological approaches. A test group (TG) received intervention implemented into regular biology lessons (10 units; n = 48); the control group (CG) participated in a basic instruction (2 units; n = 68). Both large-scale methods -- subject-matter teaching (TG) and project activity (CG) -- were compared regarding current motivation, self-efficacy, constructivist instruction, cognitive load, and practical skills. Data from n = 125 students (TG=48; TG=68) could be included into analysis (Mage=11,16; SD=.45; 55.2% female). Probability of success and interest increased, anxiety perception decreased (no group-interaction effect), whereas challenge perception remained constantly. Self-efficacy overall improved from before to after intervention, with TG reporting higher social self-efficacy and less negative outcome expectancies. No differences were found for practical BLS performance. MANOVA (after intervention) showed higher values for anxiety in TG, and for self-efficacy, CG has higher values for negative outcome expectancies (post hoc analysis). For cognitive load and constructivist instruction, no differences between groups were found. In conclusion, both methodological approaches seem to have their own pedagogical justification. Schools' implementation processes may benefit from combining (subject-matter) curriculum content with BLS information or content to facilitate time and resource-saving realization.