The extent to which education has a long-term impact on the way students view themselves and the world is a key question, not least when curricula with an international character claim to develop attributes aligned with global citizenship. To our knowledge, there have been few, if any, longitudinal studies that assess the impact of curricula that make such claims. Examining students' and alumni perceptions of an experiential element of one particular curriculum designed with this aim, the International Baccalaureate Diploma Programme, we found that some of the most marked effects stress individual benefits. This raises questions about the potential of an international curriculum, such as that explored here, to disrupt existing attitudes and behaviours in such a way as to make a sustainable better world for all.