Many environmental nudges have succeeded in increasing pro-environmental behaviors among adults, but hardly any study tested the use of environmental nudges on younger people. We conducted a field experiment involving high school students to assess the effectiveness of a nudging strategy which aimed at motivating them to power off computers when these are not used in the classroom. Our nudging strategy resulted in a significant reduction in computer power in the treated high school compared to a control high-school. We discuss the relevance of our work for research on young people's prosocial behavior as well as the implications in terms of policy-making.