In theory, at least, this isn't a problem. Hey, it's good for the students to read a book more than once, isn't it? In practice, though, you hear something like this:
"Yeah, we read that in English."
"We did that in AP, and we partnered with a class in Japan over the internet. We put it on as an opera and sang it in both languages. My teacher said that having just a male ghost was too patriarchal, so we turned Ophelia into a ghost in Act V so that there'd be gender equity and the two ghosts could sing duets together."
Okay, I'm kidding, but just barely.
Seriously, what do you do about syllabus squeeze, when you feel as though you're making choices based not on the best texts that for what you want to do in the class but on issues that should be completely irrelevant, like whether they've already read the book in high school or whether analyses of it litter the internet, thus making plagiarism a too-tempting option?
If you're idealistic, maybe you assign them anyway and hear "my high school teacher said X" or "Dr. X said this" or, worse, just see the faces of those for whom Hamlet is a been-there, done-that, got-the-t-shirt event and that they plan to reread it approximately never. Or maybe they don't do this, but it's a crapshoot.
If you're cynical, maybe you knock yourself out finding obscure texts to teach. But you know what? Some of those classics are classics for a reason, and some of them are engaging for students and important in ways that others are not.
So what do you do?