Many (bad) things have happened to our planet since PISA asked students about the environment more than a decade ago. The global temperature increased, glaciers continued to melt, coral reefs became increasingly endangered, sea levels rose about 3 centimeters, garbage continued piling up in oceans and man-made disasters, such as the Deepwater Horizon oil spill and the Fukushima nuclear disaster, have added more strains on our fragile planet’s health. Through national and international initiatives, such as the Paris Climate Conference and agreement – also known as COP21 – governments are trying to co-ordinate efforts to protect the environment; but until society is fully aware of the consequences of inaction, the cost of action may appear too high. So, are students increasingly aware of environmental problems? Have 15-year-olds became more optimistic about the future of Earth? And who are the environmentally aware students?