The study examines the effectiveness of eco-schools concerning their students' environmental values and environmental behaviour, and includes 1287 children from fifty-nine schools (thirty-eight eco-schools and twenty-one control schools) in Flanders. Controlling for effects of gender and socio-economic status, analyses show that eco-schools have no effect on the environmental behaviour of their students or on their preservation values. Eco-school students do, however, show lower utilisation values than control school students. Results furthermore indicate that preservation values and not utilisation values impact environmental behaviour. Eco-schools thus seem to be applying a pedagogical approach that impacts only on utilisation values but through that fails to affect their students' preservation values and, with those, their environmental behaviour. Directions for future research are suggested. (Contains 2 tables.)