Student engagement is a pervasive and persistent goal for educators. In previous work we have reported that activities like public real-time commenting on videos can enhance student participation and engagement . However, these events occur over a limited period of time. Thus a more challenging question is how to increase and sustain student engagement. In this paper we describe the iterative development of ClassCommons, a public commenting system with which students can post questions/comments that are shared through a public display in the classroom. The system was used in a senior undergraduate class in the spring semester of 2009. Our findings suggest that students were interested in this system. Students with different self-construal (independent vs. interdependent) appropriate this system for slightly different purposes. In the long run, we speculate that by having the teacher involved more in using this system (responding more quickly, helping structuring the discussions), it has potential for promoting sustained student engagement.