That sounds really good, OP. I was going to say also that in relation to interfering with the running of the class, the school also has a responsibility to all the other children, and the parents of the girl whose skirt he tried to look up would probably also be insisting that their child is protected.
I was also going to say that your dc showing such care towards you is really touching, and like you say a really good sign in relation to empathy.
Please can I just ask, when you referred to telling the school about therapeutic techniques, what particular things did you suggest they do with your dc?
And finally, just about PANTS, I saw the comment upthread about it being abstract. In case this is of interest, many parents I know teach the rule to their dc from about 2 years, and often reiterate it, in a very plain simple way - pointing to the area covered by the nappy or pants and saying "This is private and no one is allowed to touch this area, ever, other than me [and.. ] and if anyone does touch you it means they don't know the rule yet and then all you need to do is tell me straightaway and I will make sure the rule is explained to them, and the same applies to you, you are not allowed to touch anyone else in this area. Ok?" A 4 year old child I know told their mother that someone had touched them because of knowing the PANTS rule, and so it seems knowing the rules is a really positive thing in relation to working against abuse happening, and it can be explained in very clear not abstract terms, and not in a way which frightens the child.