I first heard about this on Twitter, and someone quite quickly posted a link to a discussion about it being a hoax, on reddit. (I am using P's laptop, and for some reason the equals sign key is not working, so I can't embed a link, but if you google "catholic school locker banned hoax" it's one of the first few results.) Apparently the poster had asked for a list of banned books on Yahoo Answers just a few days before posting the locker library story - which originally went up a couple of years ago, and has been reposted several times since.

So yes, I think your instincts are wholly correct and it is a deeply implausible list/story. Even Antonia White's convent in Frost in May didn't ban Dante, though the play version was somewhat bowdlerised version, IIRC.