With the aim to promote students' mathematics learning, we extended the Cognitive Tutor Algebra (CTA), a computer-based tutoring system for high school mathematics, to a collaborative setting. Furthermore we developed a collaboration script to support students' interactions. In an experimental classroom study, we compared three conditions: scripted collaborative learning, unscripted collaborative learning, and individual learning. After a 2-day learning phase, posttests assessed individual and collaborative reproduction of knowledge and skills, and future learning. First, with the collaboration script we aimed to improve students' interaction. Second, we assumed that due to an improved interaction students would benefit more from the learning opportunities during collaboration and, in consequence, their learning would increase as compared with the other conditions. To investigate the first assumption, we compared the interaction of a scripted dyad and an unscripted dyad. The in-depth process analyses revealed a positive impact of the script on student collaboration and problem solving during scripted interaction and in subsequent unscripted interaction. While this effect was mirrored in the learning gains of the two dyads, we could not establish a general learning effect in the quantitative between-condition comparison of student performance. Particularly for students with low prior knowledge, the removal of the script in the test phase initially entailed a decline in reproduction performance as students had to get used to the unscripted problem-solving situation. A notable finding was, however, that the collaborative conditions yielded the same outcomes as the individual condition in the individual reproduction test even though students had solved fewer problems during the learning phase and had only solved them collaboratively.