Good for you — and your son! I would have loved to have been a fly-on-the-wall when the teacher read your note. Did she try to retaliate against your son? Hope not. She knows you are watching.
We've had a few "discussions" this year and most of them revolved around me telling her that I didn't much care what her opinion was on much of anything outside of verbs, nouns and multiplication. She spent much of the first half of the school year telling us we needed to drug our kid with riddalin because he was "out of control". Out of control to her is occasionally whispering and talking during class time, talking during bathroom break, talking at lunchtime and requiring an explanation for her actions when she demands that he perform some task that others are not expected to do. In other words, he's a normal 10 year old boy who sometimes doesn't know when to shut up. He's not the perfect student by any stretch, but he's perfect to me. He uses his mind to his advantage and questions authority at every opportunity. His eyes are open to the world around him and he wants the whole story, not just the part they want to tell him.
Our last meeting ended with me asking her if it would be too difficult for her to just teach my son the academics for just a few more months and ignore her urge to criticize his personality, then we could part ways and never had to deal with one another again.
I think she got the point. Catholic school is always kind of tough, but this lady has control issues, it's very evident. She wants a bunch of drugged zombies so she doesn't have to put forth any extra effort.