This study examined the effects of guided elaboration on students' learning outcomes in a computer-supported collaborative learning (CSCL) environment. The programme provided students with feedback on their elaborations, and students reflected on this feedback. It was expected that students in the experimental (elaboration) programme would show better learning gains and that students from immigrant families would especially benefit. Two hundred primary school students of 9 different schools participated. The research can be characterized as a quasi-experimental study with a pre-test, post-test, control group design. In a multilevel regression analysis, no main effect of the intervention was found. However, there was a significant differential effect of the intervention; students from immigrant families in the experimental programme outperformed their counterparts in the control group. It can be concluded that guided elaboration in a CSCL programme through feedback and reflection is a promising approach. (Contains 5 tables, 1 figure, and 1 note.)