I've been teaching a tenth grade literature class. Aside from The Curious Incident of the Dog in the Nighttime, which I read about five years ago, I read the rest of the books when I myself was in high school. It's interesting how little I remember and how much more I think I am getting out of them now in comparison to then.
One thing I noticed is that there is a strong suggestion that Nick, the narrator of The Great Gatsby, has a homosexual encounter with the photographer he meets at a party with Tom in New York. I think there may also be several other clues supporting this, though that part is certainly the strongest.
Neither of my students even noticed that part of the book.