Many years ago I read a somewhat humorous book called "The Art of Coarse Acting" which had some useful advice on how to handle the sort of awkward situations that crop up in amateur theatre. I remember one suggestion, the way to handle things when the director is wanting you to do something really, really stupid and dangerous. You simply turn it back onto them. "I'm not sure what you mean, Richard - perhaps you could come up here on the stage and demonstrate for me how I am to 'ride the blow' when Nigel shoves the broken bottle into my face." According to the book, most such directors usually quickly decide they don't want to do it that way after all.
So if we extrapolate this - I do like the suggestion of taking difficult child along to the parenting course with you and ask for the teacher to demonstrate exactly how you are to implement the strategies they suggest, on this particular child. Or, perhaps better than taking the child - take video. Take your laptop with MP4 footage loaded on already. Wait until the best time to drop your earnest question. Perhaps just after the teacher has fatuously described how we need to learn to affirm our children for every little thing, including not killing us today... raise your hand and say, "Could you please advise us on how to implement this strategy in the following example?" and play your film. In front of everybody. Ask for feedback. From everybody. And remember - the teacher is not the problem, the people who said she was your only help - THEY are the problem. This method should recruit the teacher (and all the classmates, who may suddenly realise just how good they've got it by comparison) to your cause.
If nothing else eventuates, it should feel satisfying...
Marg