This dataset includes data collected for a PhD project, which adopts the design-based research (DBR) approach to formulate guidelines for carrying out CLIL pedagogical planning and implementation. The dataset consists of data collected from three case schools. The data include transcripts generated from interviews with teachers and students, class materials co-designed by the teachers and researcher and used during the implementation phase, and student artefacts in different forms such as posters, comic strips, food diaries,...