In traditional classrooms, a textbook was often the only source of knowledge available; in stark contrast, today's classrooms have an infinite number of knowledge sources available through the Internet. Nevertheless, a range of studies suggest that students systematically favor Wikipedia in their school-related literacy practices. The present study investigates this tendency among students in upper-secondary school, using a survey with multiple choice and open-ended questions. The main finding suggests that students favor Wikipedia because the site provides them with what they need, being fast, flexible, and easy to use. At the same time, students are aware of credibility issues associated with Wikipedia. A discrepancy between students' positive attitudes to including Wikipedia in their school-related literacy practices and their teachers' lack of approval of this knowledge source is discussed.