On the topic of "would you want her teaching your daughter" -
I had a hard time with many teachers at school. I am sure every single one of them had "thoughts" - why does she behave like that, what is she wearing, did she really just say that, whatever next? And that's fair enough! I was not always the easiest, cookie-cutter child, for various reasons both internal and external. I can't imagine for a second that a single teacher thought "What a straightforward, unspoilt pupil; just how I'd like a daughter of mine to be, no worries at all about that one".
However, it was very clear to me when a teacher cared or not. Some teachers treated me with suspicion and dislike the entire time they were teaching me. A few teachers seemed to take no interest in any of their pupils at all. Other teachers, even if they were strict, took the time to see the whole child, and noticed where I needed encouragement and support. It seems clear that KC is the latter kind of teacher. She knows her pupils are children, not adversaries.
I've always hoped that my children get teachers of the latter type too. I am sure some of their personality traits might get up the noses of some teachers, as we are all human, but I dread them being taught by thoughtless teachers who can't get past the first impression.
I can't imagine begrudging any of my former teachers if they wrote an honest memoir that included a composite character like me, describing how they overcame their first impression and saw the child's struggles and potential. I mean, sure, if they sent it to me with a note saying "The difficult girl in chapter 4 is you!", I might feel uncomfortable.
Full disclosure: I have read excepts from the book and the related "long read " by KC linked upthread, but have not read the entire book.