Well, there's no need to argue over that.

[ Her voice sharpens as she addresses the students. Full Stern Professor Mode - and she can certainly be stern when she likes. ]

You're both adults, you can reach a compromise like adults. In the mean time, you're wasting time and causing problems. Furthermore—

[ ... She looks inclined to continue, without realizing that she might just be on her way to making them feel bad. Well, it would stop the argument, but...? Maybe you've accidentally wandered into a good cop-bad cop situation, here. ]