So who defines it? The person assigning the books?I know, and that's where those who wish to censor can get the thin edge of the wedge in. That's why the price of freedom is eternal vigilince. Determining community standards cannot be allowed to be an excuse for censorship and other violations of our first ammendment rights.
I agree, one should be allowed to read whatever book they choose, but I don't think that creating a standards for assigned reading is the same thing as censorship.
For instance, removing the book from the library would be bad, but being able to select a different book from a list to read would be good. More choice is better than forced acceptance.