Maybe more WWYD than AIBU...
DS started nursery in September and has loved going in, teachers seem lovely.
We was playing "school" last night and he got to be the teacher. We gathered all the teddies to be other students.
He was mimicking all the things that I can imagine his teacher does in class and it was brilliant until little teacher then says in a sentence "...fxcking dxckhead childrens..."
I asked what did you say? And asked once more just incase I really did mishear him. I asked where did he hear that from? (Neither me or his dad say f'ing d'head, he doesn't watch YouTube, no other people are around him such as other family we don't live close to them).
He says Mrs XXXXXXX said it, his school teacher. I said really? when did she say that?
He just said yeah and repeated the phrase again.
I'm pretty sure I can tell when DS is lying as he will laugh straight away and then says the truth and it didn't seem so as he had no reaction after saying it was his teacher.
I'm not sure how to address it with teacher without accusing her? Would she be offended? Is it even something I should address? I feel like so but don't know if I'm overreacting... first time mum 
We've had the discussion about not using it again and he nodded. Should it end here really?