Managing the learning environment is both a major responsibility and an on-going concern for every teacher, even those with years of experience (Good & Brophy, 2002). There are several reasons. In the first place, a lot goes on in classrooms simultaneously, even when students seem to be doing only “one” task together. Twenty-five students may all be working on a sheet of math problems. But look more closely: several may be stuck on a particular problem, but each for different reasons. A few others have worked only the first problem or two and are now chatting quietly with each other instead of continuing. Still others have finished and are wondering what to do next. At any one moment each student needs something different—different information, different hints, different kinds of encouragement. The diversity increases even more if the teacher deliberately assigns multiple activities to different groups or individuals (for example, if some are doing a reading assignment while others do the math problems).