How does visual communication in multi-user educational 3D environments support interaction and collaboration? To what extent does it affect learning? How can it be improved? We investigate the role of visual communication in 3D virtual reality basing on our 8-years experience of VR-based educational projects, tested with good results by thousands of users from 17 countries. We identify 3 key aspects strongly related to the visual nature of VR, contributing to the success of collaborative experiences: virtual presence, proxemic semiotics, and peripheral awareness.