It’s graphic, I grant you - of course it’s only right to feel strongly about it, and absolutely it should be taken up with other parents and the school.
On the other hand I got subjected to Gloucester in King Lear having his eyeballs gouged out extremely graphically on stage. If memory serves, I’d been too slack to read that part of the play beforehand, so it was a real shock! not to mention Lavinia in Titus Andronicus being having her hands cut off and tongue cut out.
blecch
And I can assure you, while most 16-17 year old girls aren’t reading graphic descriptions of child abuse on their own, plenty of them ARE reading, in some of the commonly-available teen magazines and other reputable publications like Cosmopolitan, graphic descriptions of how to give good blow jobs, erotic short stories and things like that.
God forgive me, I know I did,

and I can’t imagine it’s less prevalent today. You’d rather they read about such things under parental and teacher supervision where the issues can be openly discussed, or behind your backs as most things are read?
And of the two I don’t know that a description such as Morrison’s mightn’t be preferable. Sure, it’s graphic and it depicts the warped mentality behind child abuse, but in no way does it glorify it or make it seem attractive, and would certainly get anyone who read it thinking about the issue of child abuse.