Censorship is when the government prevents you from reading something. This is "choosing curriculum". As best I can tell, the book is not banned from the premises.
The bible is a great example of a book that is truly censored in public elememtary schools.
Censorship only applies to adults. It is not censorship to keep playboy out of schools. It IS censorship to keep it out of stores.
You can keep ANYTHING out of schools and it is not, by definition, censorship.