Empowering students to act in an environmentally responsible manner is being increasingly touted as a central goal of formal environmental education. Acting in a responsible manner requires the development of environmental knowledge as well as positive attitudes and values towards the environment along with other attributes. While some guidance about how to plan and teach environmental education is available in curriculum and policy documents, teachers are often either unfamiliar with such documents and/or unaware of the theories and pedagogy of environmental education (Cutter-Mackenzie & Smith, 2003; Eames, Cowie, & Bolstad, 2008). This paper offers a definition of environmentally responsible behaviour and identifies the role that knowledge could play when environmentally responsible action is taken by students that could be useful for teachers. Three different lenses are used to examine the knowledge developed by 11-12 year old students and their subsequent actions during engagement in an environmental education programme (n = 22). The lenses consist of a cluster of types of knowledge developed by Jensen (2002), a framework for analysing understandings of sustainability and the type of actions taken (Jensen & Schnack, 1997; Kollmuss & Agyeman, 2002). The results suggest that these students developed different types of knowledge that informed the actions taken and that their actions can be categorised as action competence. It is also suggested that these types of knowledge need to be taught explicitly. A three part model is then proposed that could assist students to learn about the nature of action, enabling them to work towards potential solutions for complex environmental issues. (Contains 1 endnote, 1 table, and 2 figures.)