Gawd, I have actually just done it anyway, but I have the fear (slightly). Not the fear of being wrong I am never wrong, more the feeling that correcting the teacher is not quite the done thing.
Anyway, she wrote "wack" for my son to copy. Now, I have never heard of whack (I'm presuming) being spelled this way, so I googled it and it does exist, albeit as some kind of American, tut slang, as in "She looked wack". -This is a compliment, apparently.
Whilst writing this, I have realised that there are two strands to this AIBU. First, as above. The second is AIBU to be such an old gimmer that I do not realise that street lingo is all da rage. In Cornwall. Amongst primary school teachers.
Go on then, tell me what you think.