A considerable literature looks at universities' approaches to integrating sustainable development into teaching and learning, but less is known about how Education for Sustainable Development (ESD) affects student attitudes, values and norms. To our knowledge, only a few studies have quantified such effects of changes in curricula. This study contributes to this literature by quantifying and measuring the effect of a compulsory sustainability activity on students' ethical and moral perceptions. Our results show that ESD can indeed affect moral perceptions of what constitutes socially appropriate behaviour, but not in a homogenous way. Instead, the effect varies with background characteristics of the students.