I've just popped into school to say as much to the teacher. I said I can only assume he was unaware of what it stood for? 
He was unaware but apparently it's also the name of band so he thinks it's OK for the children to self-censor in this situation. I'm not so sure
I think he'll end up with complaints from parents and possibly other teachers too if he displays these posters in the corridor.
I wasn't complaining, as such, because if he didn't know what it meant then how could he say not to use it and I can see his argument about the children being given the opportunity to decide what's appropriate and what's not but at the same time fucking is a pretty strong word for primary school art!