We have these people who go to college and get specialized degrees so that they can do things and work in school libraries and figure out what books are appropriate for the school.
You might have heard of them. They're called librarians.
Deciding what books do and don't belong in a library is literally part of their job. I know, because I'm married to one. She used to work in a school library, now she works in a public library. It was a Catholic school (she's an atheist, they didn't discriminate) and they trusted her to figure out which books were appropriate for their kids because of her degree. What does that tell you about librarians?