ask “what do you think we should do?” The answer might be there already.
For anything else tried, ask permission from your child before doing them. Why? Because: they are the ones that have to deal with the consequences of your decisions, not you.
You can go up or down the chain, from dealing directly with the bully or parents or teacher or school.
Or sideways, coordinating a plan with his/her friends (if any).
Or switch schools. New school = new problems but it definitely eliminates the one particular problem. Just because “you take you wherever you go”, DOESN’T MEAN the child will be bullied in a new school.
Bears repeating: keep your kid in charge of the whole process. They might decide “it doesn’t matter anymore and things are fine”, which is their choice. Then again that might be a cover so they move back to “kid code” (what happens in school, stays in school and you don’t bring in parents EVER) so you’d have to watch out for that.
Standard confidence builders like karate, mixed martial arts, whatever’s available in the area are also possibilities.
And can’t forget this one: Maybe the child was antagonizing the other and the other child isn’t actually a bully but rather BEING bullied by your child and was acting out.
I say all this knowing nothing about what I’m talking about because I never had kids of my own. But as somebody who was REALLY glad to get out of public school (one of he reasons was bullying, although mostly generalized anxiety, and I took the initiative to find a school where I could apply for a scholarship, got the backing of my mother, entered the contest (essay writing) and took some tests, and got it… and it worked because *I* wanted it. [8th grade was public school, high school was private]
That’s why “keep your kid in charge of the decisions” is so important. Bullies take control away from people. But a parent that empowers GIVES control back.