This paper argues that for the study and facilitation of collaborative learning, existing theories of grounding such as that of Clark and Shaefer [5] cannot be applied without adjustments. When comparing collaborative learning and conversation, four dimensions can be identified where grounding at a knowledge level differs from the grounding at an utterance level. Firstly, the indirect access and the existence of a range of manifest meanings, poses the need for a notion of `groundedness'. Secondly, we propose providing evidence in `co-referenced actions' to be an important process as well as an additional marker to assess grounding. Thirdly, instead of simply repairing misunderstandings after they arise, `perspective taking' becomes a more prominent mechanism. Fourthly, effort into grounding is turned from needing to be minimised, into needing to be `optimised'.