When I have taught 2 sections of the same course in a given semester, I can often notice group effects -- one section may be on average noticeably more engaged, and tends to do better on exams. I am sure there are many reasons for that. But this semester, that gap is significant. The first section can easily be quiet, not respond to questions, and then have a pretty unremarkable exam average. The second section on the other hand, is full of questions that make me struggle to finish everything I want to cover (which is a good thing - so I plan for less in each class, which leads to class finishing ~10 min early at times in the first section, but barely getting everything in the whole class for the second section), and on exams, half of the class in section 2 finishes anywhere from 10-20 minutes early, and their average scores have been 10 percentage points higher than the first section consistently.

This just seems uncharacteristically large, but maybe this type of thing happens more often than I expect. I did suspect maybe section 1 informs section 2 about the questions that would arise on the exam, but the level of engagement in class also does seem fitting with a 10p.p. gap, so even if that is happening, I think it would explain a small part of the gap. Wondering about others experiences!