There is a huge difference between what a parent says and does within in a home setting and what is 'out there' in the general society and media.
As we grow up our parents thoughts, attitudes and rational make a huge difference in how we learn to value and judge the world.
I am not saying that we grow up to accept what our parents say is correct or even vaguely valid but their values to affect us. We might eventually reject everything our parents have ever valued but that in itself is a reflection on how we were brought up.
I do feel that it is a parents job to make valued judgements on what is 'normalised' within the home. Thus its perfectly acceptable, in my view, to discuss elements of sexuality with children as they grow and develop. I was always guided by what they asked about, always answering, as directly as I could, the immediate question. I did not however, expand upon a subject if it was not part of the initial enquiry.
We discussed much at home but I would never have agreed to my child going to school dressed as a character from an 'adult' book. I do not see that as hypocrisy. The books were of little literary merit, they normalise a sexual preference that has little to do with stable family relationships or loving adolescent relationships. There is not even the 'tongue in cheek' humour of a Roger Moore type James Bond Character to redeem it. (Ian Fleming might not be to everyone's taste but he is a far better author and few teenage boys see James Bond as anything other than an action hero in a fast car and smart suit).
I'm with the school on this - they had a duty of care to the other children and their parents.