April, Disingagement can happen for a lot of reasons: unprepared, do not understand, tired, bored, have fallen behind, illness, or distracted by other thoughts. In all cases (except possibly illness), we can reingage by simple to aggresive methods. Just circulating about the room keeps students a bit more attentive. Asking questions frequently also keeps students attentive. Sometimes, it's necessary to change the activity in order to keep interest. That can occur with a plan to return to that activity later on in the class period. Sort of back and forth, which is a form of variety. Getting students actively involved is probably the best way to keep students engaged, and there dozens of ways to achieve that depending on the class, the topic, and the level of instruction required. Barry Westling