Our pupils' generation will eventually have the daunting responsibility of making decisions about local and global biodiversity. School provides an early opportunity for them to enter into formal discussion about the science and values associated with biodiversity conservation; but the crowded curriculum offers little time for such activities. This article outlines a successful approach to engaging pupils in decision-making about conservation scenarios, enabling them to share and develop their views within a short space of time. The discussions were managed and assessed by science teachers, and their opinions about the practical value of the sessions are also presented. (Contains 2 figures.)