When my son was in the 4th grade, we had a similar issue. I was on a fist name basis with most of the school staff because I spent almost as much time in the principals office as my kid.
Finally, in a student teacher conference, I told the teacher that was giving us all the grief, that if she didn't ease up, I was going to make it my mission in life to get her job. At first, she was skeptical but after a week of me calling the school superintendent with daily reports of her nonsense, she backed off.
I hope that you're able to resolve this. It's very stressful for the whole household.
Gary