Empirical data on early network history are rare. Students beginning their studies at a university with no or few prior connections to each other offer a unique opportunity to investigate the formation and early development of social networks. During a nine week introductory physics course, first year physics students were asked to identify those with whom they communicated about problem solving in physics during the preceding week. We use these students' self reports to produce time dependent student interaction networks. These networks have also been investigated to elucidate possible effects of gender and students' final course grade. Changes in the weekly number of links are investigated to show that while roughly half of all links change from week to week, students also reestablish a growing number of links as they progress through their first weeks of study. To investigate how students group, Infomap is used to establish groups. Further, student group flow is examined using alluvial diagrams, showing that many students jump between group each week., Finally, a segregation measure is developed which shows that students structure themselves according to gender and laboratory exercise groups and not according to end-of-course grade. The results show the behavior of an early social-educational network, and may have implications for theoretical network models as well as for physics education.