Computer Supported Collaborative Learning literature relates high levels of collaboration to enhanced learning outcomes. However, an agreement on what is considered a high level of collaboration is unclear, especially if a qualitative approach is taken. This study describes how methods of Social Network Analysis were used to design a collaboration index. The study was conducted in a heterogeneous context of hybrid and online courses, in  a virtual classrooms system, in higher education. Results show that the collaboration index effectively identified levels of collaboration in asynchronous discussion forums.