This study aims to investigate how students mobilise scientific and socio-political knowledge about climate change in communicative actions directed at the public. It presents a teaching and learning proposal for high school science classes, focusing on critical communication and action in the context of climate change. Grounded in the Science-Technology-Society (STS) framework and Cultural-Historical Activity Theory (CHAT), the course aims to help students learn scientific knowledge about climate change while fostering critical agency to address socio-environmental challenges. The course, implemented with 37 high school students in São Paulo, Brazil, was structured into two phases: (i) one focused on foundational scientific concepts, historical context, and socio-political dimensions of climate change, and (ii) the other emphasising student-led interventions to communicate and act on the issue. Activities included lectures, group discussions, and projects such as creating social media campaigns, producing documentaries, and developing educational games. The data presented in this study comprise the didactic sequence of the course offered to students, along with the final reports they produced, which contain descriptions and analyses of the educational interventions they implemented. The findings highlight the importance of integrating scientific, political, and ethical dimensions in climate education, enabling students to understand the complexities of climate change and develop transformative agency.