There's a TV... thing that bothers me. I can't really call it a trope, because my extensive research (2 hours on tvtropes.org, most or which was spent clicking links from the Supernatural page) only turned up two actual examples, though I know I've seen it more than that. I cannot stand it when people in shows/movies/books/what have you demonstrate what a social pariah they are by eating their lunch in the bathroom. My issue with it is threefold:
1) I've been the new kid. Unless you smell, making at least one friend by lunchtime isn't really that hard.
2) You know what's not a good way to make new friends? Becoming the girl who eats on the toilet. "Does she have some sort of intestinal issues?" your new peers will wonder.
3) People. Poop. In. There. I don't bring open containers of food into the bathroom. Seriously. If I buy a soda, take one sip and have to pee then that soda is over. Because there are some things you just don't come back from, and drinking toilet soda is right up there getting vomited on by an adult.
Additionally (and I recognize that I should have counted this as one of my issues, but I couldn't pass up a chance to say "threefold"), how small does a school have to be for there to be no viable empty table, or floorspace, or anywhere where someone isn't peeing within two feet of your snack pack?
I could go farther with this, but not without veering directly into "crazed germaphobe" territory. Instead I'll just close out by saying, if you've never been to tvtropes.org, go now. search for any show of movie, start clicking links and watch the day slip away.