Hi Robin: For me, it seems that students get disengaged because they're unprepared, unfamiliar with the material, bored, tired, ill, or distracted. Whatever, getting them back on track can be simple (as you've described), or employing "change-ups", such as changing gears completely, and doing a wholly different activity. You describe group discussion. I think this one of the best ways to get students "activated" and motivated. Also, it fosters critical thinking, public speaking, class participation, self confidence, competence, and often, analysis. These are good traits to develop, and in a discussion forum, they're fun to cultivate. Regards, Barry