PeerWise is a system in which students create multiple choice questions and answer those created by their peers. In this paper, we report on some quantitative results which suggest that students who use PeerWise actively perform better in final examinations than students who are not active. We note a significant correlation between performance in written (not just multiple choice) questions and PeerWise activity, suggesting that active use of the system may contribute to deep (and not just drill-and-practise) learning.