You need to march right down to that school and try and get her fired! Well, she won't get fired but she will have learned a lesson and will then treat your kid with the utmost respect and love! Just like when a similar situation happened to me when I took 3rd place in the Central Elementary spelling bee (the only 4th grader to even get out of the first round against two 5th graders!) and the teacher that had beaten my headd against the brick wall and had scratched my chest just a few months earlier and mom tried to get her fired for it gave me a teddy bear as a guilty "consolation" prize. (I will never forget that fake smile either - I knew what she tought of me for sure, though she really was sorry!)
Remember though that sis in law works there too, is her teacher and whatever sh(i)t-storm you brew will come back around to you!
UTROY
Proverbs 21:19 (why I hunt!)