Teachers play a major role during CSCL by monitoring and stimulating the types of interactions between students that are conducive to learning. Teacher dashboards are increasingly being developed to aid teachers in monitoring students' collaborative activities, thereby constituting a form of indirect support for CSCL in the classroom. However, the process of how teachers find and interpret relevant information from dashboards, and which help they need during this process, remains largely unexamined. We first describe how we arrived at the design of a prototype teacher dashboard in the context of primary school fraction assignments, based on teacher interviews. We then report an experimental study (n = 53) to investigate the effect of the type of support a teacher dashboard offers (mirroring, alerting, or advising) on teachers' detection and interpretation of potentially problematic situations where intervention might be needed. The results showed that the type of support did not influence detection of events, but did influence teachers' interpretation of a CSCL situation.