Back when I was in college, I did some part-time work as an editor for high school English essays. Basically, I'd read essays and mark up all the grammatical mistakes and other errors, then I'd assign a grade. I did this all in pencil, then I handed the essays to the teacher, who reviewed them before coming up with his final grade.
One time, the students wrote about Edgar Allen Poe's A Cask of Amontillado. I've never read the story, myself, so it was interesting reading 200-300 essays on it. The topic was "Is the narrator sane or insane?". Half the essays said he was sane, and half the essays said he was insane. I thought it was interesting how the students were divided along the middle.
There were about four different quotations which showed up in about 1/3-1/2 of the essays. I'm guessing these quotations were on a handout, or discussed in class, or something like that. One quotation, in particular, describes how the narrator planned his murder in great detail. Half of the students thought this was proof of sanity ("how could a crazy man make such detailed plans?"), and half of the students thought this was proof of insanity ("how could a sane man make such gruesome, detailed plans?"). Again, the students were divided along the middle. Rather odd.