Abstract Background Children and youth increasingly seek for health information on the Internet and Social Media, requiring to link media, digital and health literacy to equip them with the skills to distinguish reliable and trustworthy information from disinformation. Preferably, health literacy learning is addressed in schools, but to date there are no programs to address this subject in German schools. This study sought out to develop a classroom-based toolbox to promote health literacy in, e.g., media and digital education classes or subjects such as biology, physical activity, social sciences. Method A review on curricular, school requirements, and health literacy interventions was conducted. Findings informed the participatory development of a health literacy toolbox with teaching and learning units for students (7-8th grade) and teachers. The toolbox was tested in three schools, comments were received by teachers and students, supporting the adjustment of the toolbox. Results The toolbox is based on the school curriculum for media and digital education of secondary schools, addressing adolescent students in grades 7 and 8 in German secondary schools. It includes learning units to increase competencies regarding health information seeking, understanding of information, and critically analysing health claims and messages. Alongside exercises on critical thinking while navigating online Internet and media sources, the toolbox provides topical learning units, linking health literacy with, e.g., COVID-19, vaccination, healthy eating, substance use, media use, commercial determinants, and mis- and disinformation. Conclusions This is the first health literacy toolbox of its kind. Embedding it into the mandatory media and digital education curriculum, and addressing both students and teachers, will ensure the uptake of the programme in schools. Both the toolbox and the methodology of its development can serve as a blueprint for other countries to develop their own interventions.