Never before have the stakes been so high for the role of science education in shaping how people interact with the environment. Human activities responsible for the production of greenhouse gases, the accumulation of waste, the fragmentation or destruction of ecosystems and the depletion of resources are having a substantial impact on the environment. As a result, threats to the environment are prominently discussed in the media, and citizens world wide are increasingly faced with the need to understand complex environmental issues. Environmental science and geoscience continue to generate comprehensive and complex knowledge. Therefore, the challenge for education is not only to produce more and better trained environmental scientists, but also to support informed and motivated citizens who are capable of understanding, interpreting and acting upon sophisticated scientific theory and evidence. The OECD's PISA 2006 assessment of the science competencies of 15-year-olds offers the first comprehensive and internationally comparative knowledge base of students' knowledge about the environment and environment-related issues. "Green at Fifteen?" presents an analysis of this knowledge base, including information on the sources of students' awareness of environmental science, their attitudes towards the environment and how these attitudes interrelate with their performance in environmental science.