I frequently teach CS1 and CS1-and-a-half in a very diverse, working-class, commuter public sector college. I have my students to work in small groups (2 or 3) on their larger homework programming projects. The students rarely know each other from outside class, and I take it upon myself to assign them to the groups. With the best of intentions and considerable misgivings I use demographics and to-date academic performance to construct the teams: same gender, different ethnic background, similar academic performance. This seems to "work" but maybe that sense is merely expectation-fullfillment.

Do others use these criteria, or opposite ones? I'm curious to learn of others' experiences and possibly perspectives I haven't considered.