This paper reports on a study of teacher support in experimental computer-supported collaborative learning (CSCL) settings where students engage with graphs in real-time labs within the context of school science. Real-time labs are digital devices and software connected to student-controlled sensors or probes that can measure and visualize data graphically. The empirical setting was a science project about ocean acidification (OA) where lower secondary school students conducted measurements of the pH value of water with increased concentrations of CO[subscript 2]. The analytical focus is on student-teacher interaction during group-work activities where the students carried out, reviewed and reported on the real-time lab experiment. The analyses show that students needed additional support from the teacher in interpreting the real-time graphs and in making connections between the graphic representation, the practical undertakings of the experiment and the underlying scientific phenomena. Most importantly, the study demonstrates the complexity of teacher support in CSCL settings and how this type of support intersects with the support provided by digital resources, peer collaboration and applied instructional design.