Abstract : With laptops, mobile phones, tablets and broadband wireless access becoming more widely available, Web 2.0 is now entering schools. This changes the way students work and communicate, altering their relationship with knowledge, and generating new objectives for media literacy in the digital society. Thus, schools face new challenges and this paper aims at highlighting four of them. A first challenge relates to trust. Web 2.0 opens the classroom to the world and educators have to face new dangers and irrelevant uses, while bringing their students to gain better access to information and culture. The second challenge relates to teachers' professional identities. The role of teachers is changing as Web 2.0 tools are begin used by students and policymakers should take this into account. A third challenge relates to a growing need to control working time, timetable organisation and rhythm in schools. The fourth challenge that we underline is the need for common rules that allow the students to benefit from the opportunities offered by Web 2.0 to develop their autonomy and to foster ethical practices.