This paper explores evidence from prior research already conducted in the field of use Web 2.0 in educational institutes. The aim is to check if social media can be integrated in formal education. The analysis is structured by drawing on the well-established model by Rogers called Diffusion of Innovations. Based on the theory, an Online Educational Social Network, Edmodo, is presented and used in students of the highest level of Greek High School (3rd class of Lyceum), in the subject of Physics, to examine how social media in schools fit the diffusion of innovation theory. The conclusion is that Edmodo can be adapted as an educational tool as it offers to students the required skills in order to perform effectively in Information Society.