I work in teaching so I can relate to your experience.

We attract mostly students of average moral fiber, with a smattering of self-important, high-maintenance assholes.

I'm sure mental illness plays a part, as a lot of these people are clearly intellectually under-equipped to follow any type of instruction or engage in any task requiring more than five minutes of continued concentration, but every now and then I come across some entitled douche bag who thinks they can get away with anything just because they're paying for the lessons.

You haven't seen the disgusting underbelly of the human psyche until you've had to slave away in a customer-facing job of some sort.

I'm not exaggerating when I say it has turned me into a bit of a misanthrope. It has made me a lot less trusting of people, I can tell you that.