So I teach a discussion/recitation section at my university for an undergraduate statics class. I have two sections of 24 students each, and they each need to be 50 minutes. I am supposed to use the time to ask the students if they have questions about the homework, lecture, etc. Usually one or two students will ask a homework question and I will work out part of the solution and then they will say they can take it from there, and then nobody else will ask anything. So I started putting up homework problems on the board, making them get into groups to solve them, and then bribing them with candy if they write up their solutions on the board. The problem is that all of this usually only takes about 35 minutes, and since nobody will ask any questions that means they all understand everything, right? So I was letting them out about 15 minutes early. Now somebody actually complained to the professor that I was letting them out early (who does that, seriously?) and the professor told me I need to use the whole time. And....go.