Am I getting the feeling you are saying the teachers aren't too happy when they see your child back in school again? Am
I reading that right?
Speaking from a teacher point of view, if a child is in nappies and needs a lot of support, then this will take up a lot of the TA's time. Does your child have a 1-on-1 TA, and the class have another TA? Or does the same TA help your child and the class?
If it's just the one TA for everyone, then this can become wearying when the TA has to repeatedly go and change/help your child, when perhaps they were in the middle of hearing a reading group for example, or in the middle of taking a group for painting, etc.
Perhaps the reason they aren't looking happy at your child being in school is because it might be quite a lot of work looking after them.
I don't mean this to be harsh, I really don't, I'm just giving another perspective.
On the other hand, I don't agree with the teacher at all; they should be professional and polite to everyone and not 'hmmm' like you mention. I am not sure why they are not calling you when they see runny nappies, I would have if I was your child teacher.
Happy to answer any other questions, please don't take offence at what I've said,