From the excellent education blog, Clay Burrell asks why controversial topics are allowed to be touched on in chronologically distant literature – incest in Hamlet and Oedipus the King, underage sex in Romeo and Juliet – while modern literature on similar topics is unwelcome in the school library. 

Topics like teen pregnancy, abusive relationships, and peer pressure are exactly the kinds of things we should be discussing with our teensto prepare them for the world which they will face but any literature that is in a modern setting seems to provoke fear in some parents.

From the comments; 

We choose to be (un?)witting accomplices to daily contemporary tragedies by only teaching the ancient, irrelevant ones.