Today during two of my classes as the respective professors neared the end of the allotted class time, my ears perked up at the mention of two words: next class. The worst part was that these teachers weren't saying that they would "see you next class." Instead, they mentioned something they would be discussing during the next class period despite the fact they were not yet ready to end the current class.
As a student who is bored to death in a class I am required to take, that's just the worst thing a professor can do. I hear the words "next class" and the assumption is that we have reached the point where it is okay to break until our next session. Example:
"While it is important to realize the focus of market failures, that is something we will discuss next class."
At this point, the sentence I know I was expecting sounded something like this:
"But that's it for today. See you Thursday."
"But what we do need to understand now is that..." and continue on for another 20 minutes.