This article has both theoretical and practical purposes. It starts with a project-orientated and axiological identification between education for sustainable development and global citizenship education. It then recalls the importance of the sense of responsibility in constructing identity and knowledge. To best construct a sense of responsibility, the article proposes to measure the relevance of education in commons, as it has been redefined and theorized by political and economic scientists following the work of Ostrom (1990). After clarifying the definition of these commons and how they can be used in educational methods, the article describes an experimental protocol set up within the foreign-language curriculum of an international school.