Is this going to be on the test?
That one student with attitude who slumps in his seat (it is almost always a "he") and gets the slightly impatient what-am-I-wasting-my-time-on-this-for look and starts the attitude through body language.
Sometimes, just to prove he is paying attention he'll make a generic comment at the beginning of class, but as the others sit up straight and start interrupting with questions and comments he slouches further, starts fidgeting, looking out the window, furtively checking his watch.
This wasn't what he came to university for, he wants to hang with his buds, go to some games, get the credentials to make some real money; this class isn't even part of his major, just some requirement that the university makes him go through the motions for.
Most of the time you never get that students attention, sometimes you can find the button that gets his attention, makes him sit up, think "I didn't know that", maybe even a "wow"... everyone else is involved, concerned, thinking critically, looking for new angles, trying known approaches to solve the issue. He doesn't care, he's looking forward to the weekend, or spring break. Just get it over with, nothing important happens at university anyway, it is just a ritual to endure to please the parents and have the right creds.
Gotta keep trying to get through to those students though, some of them end up in positions of responsibility.