Is it just me, or does there appear to be a high concentration of clever little bastards around these parts? And I find it very heartwarming the real concern shown by folk, particularly the parents, of course, over kids potentially underachieving or losing interest in learning.
I actually pretty much stopped working in school when I was 7, because I considered that the work was boring and I didn't need to do it. By the time I was 8, it had evolved into a bit of active defiance, and I spent most of the time separate from the class, sitting at a desk beside the teacher, twiddling my thumbs and daydreaming most of the time. I still passed all the national tests with the rest of the top tier of the class - and so was left just coasting…
A few months back my five-year-old nephew, in his first year of school, was complaining that school was boring, and he was being taught things he already knew. I wasn't sure how seriously to take these comments, and decided just to bear them in mind, have a word with my brother about it and play it by ear. He hasn't complained recently, and made some innocent remarks about a "reading club" he's in with another boy, where he reads slightly harder books than with the rest of the class - and at his recent parents' night, the teachers (there are two teaching the class) said that he is currently reading at the level of someone at the end of their second year of school, and one of the hardest things to do is keeping him challenged.
That was encouraging, that they acknowledged his potential and had it well on their agenda. I'd have fretted like hell if he had the sort of arsepiece of a teacher as mentioned in the OP. Honestly, I'd have sat brooding and wringing my hands over it for ages - and in my case it's actually a bit worse because I'm just an auntie and can't have much direct influence. It's dreadful that any kid should have their potential stunted in any way by some git or other - and as has already been said, there are some teachers out there who clearly haven't selected the proper career path for themselves…
So along with my relief over my nephew, you have my empathy and best wishes for your daughter, Durro. Glad to hear that things have improved, and that the teacher seems to have made some conscious effort to improve. She may have been having some unseen emotional difficulties herself that were making her teaching style especially bad - but that's not your job to speculate on or just put up with. You did well to spare her the showing up in front of her seniors, and the important thing is that she has improved, at least to the point of adequacy.