This paper reports on a case study of the teacher's role as facilitator in computer-supported collaborative learning (CSCL) settings in science. In naturalistic classroom settings, the teacher most often acts as an important resource and provides various forms of guidance during students' learning activities. Few studies, however, have focused on the role of teacher intervention in CSCL settings. By analyzing the interactions between secondary school students and their teacher during a science project, the current study provides insight into the concerns that teachers might encounter when facilitating students' learning processes in these types of settings. The analyses show that one main concern was creating a balance between providing the requested information and supporting students in utilizing each other's knowledge and understanding. Another concern was balancing support on an individual versus group level, and a third concern was directing the students' attention to coexisting conceptual perspectives. Most importantly, however, the analyses show how teacher intervention constitutes the pivotal "glue" that aids students in linking and using coexisting aspects of support such as peer collaboration, digital tools, and instructional design.