The advent of networked environments into the classroom is changing classroom debates in many ways. This article addresses one key attribute of these environments, namely anonymity, to explore its consequences for co-present adolescents anonymous, by virtue of the computer system, to peers not to teachers. Three studies with 16-17 year-olds used a vote-debate-vote scenario to explore in Study 1 (N = 59) anonymous, public or private voting with public oral debate; Study 2 (N = 79) anonymous, public or private voting with public written debate; and Study 3 (N = 84) anonymous or public voting and debating. Students were more likely to change their views after debate and show less convergence to group norms if voting anonymously. However, anonymous debate created an increased amount of off-task behaviour, but only at the beginning of the lesson. In general, anonymity was found to bring positive benefits to classroom argumentation. (Contains 3 figures and 8 tables.)