This paper tests whether variations in class size cause teachers to alter their teaching methods. Examination of 2,170 math classes suggests that when class size is reduced, teachers do not spend more time on new material, nor do they finish more of the assigned textbook. Rather, teachers shift time away from group instruction and towards individual instruction. Time spent on student discipline and routine administration declines modestly, while time spent on review rises. Even large reductions in class size shift teachers' time allocation by only a few percentage points.
Teachers react more strongly to class size changes when teaching below-average students.