Our child was similarly picked on. I'm normally direct and blunt. Professional but blunt. I let the principle know it should stop.
We were informed that our home environment was likely the problem and that the school was requiring us to go to see a school paid counselor.
A friend was a psychologist qualified to do the review and told us all to come on down to his office. We did. He wrote a letter to the school to correct its behavior. In other words, telling the principle his school was the problem.
That put an end to their assault on our family but incredibly it did nothing to stop the abuse of our child by the other children.
I had warned the principle that I would get a lawyer. We did that. Turns out the school had another suit against it over the very same thing. I was called into the principles office and given assurances they would correct the situation.
It did get a bit better but still the hurt was there. And what was most apparent was that the teachers and the administrators were as childish as the kids were. I also wonder what would have happened if I had not had a friend to intervene on the sociological review.
I am glad you were able to get the situation under control. My daughter only spent a year in public school (my son is autistic- in public middle school- and if he is teased, he is luckily oblivious.) She had a bullying problem that was not resolved in that year. The one time she fought back, she was disciplined. I have a real problem telling my child that fighting back is wrong. She is back at the private school now. The bullying still happens from time to time there, but the school is more responsive than the public school was.
It takes a lot of hits to the self esteem to be bullied. I grew up in a non-dysfunctional home, but I have had to work really hard on my self-esteem as an adult- and that is a result of school not my family.
I did see a good therapist (after I married someone who ended up a bully) that helped me see the kids who were so mean most likely had their own problems at home.
You being there for your child will negate a lot of the ill effects.