Computer-supported collaborative learning (CSCL) scripts can foster learners' deep text comprehension. However, this depends on (a) the extent to which the learning activities targeted by a script promote deep text comprehension and (b) whether the guidance level provided by the script is adequate to induce the targeted learning activities effectively; both may be moderated by the learners' prior knowledge. Inspired by the ICAP framework (Chi and Wylie in "Educ Psychol" 49:219-243, 2014), we designed a low (LGS) and a high guidance script (HGS) to support learners in performing interactive activities. These activities include generating outputs that go beyond the text, while simultaneously referring to the co-learner. In an experiment, 88 undergraduates were assigned randomly to either the LGS or HGS condition. After reading a text paragraph, LGS participants thought about discussion points for the upcoming collaborative discussion, while HGS participants were (a) prompted to generate outputs individually that go beyond the text and (b) exchange them with their co-learner to provide information about the co-learner's comprehension state (awareness induction). Subsequently, dyads in both conditions discussed the paragraph in a chat to improve their text comprehension. Prior knowledge moderated the effect of the script guidance level on deep text comprehension: low prior knowledge learners benefitted from the HGS, whereas high prior knowledge learners profited from the LGS. Moderated mediation analyses revealed that these effects can be traced back to patterns of learning activities which differed regarding learners' prior knowledge. Based on these results, possible directions for future research on CSCL scripting and ICAP are discussed.