Yes, here is a way to do it (not theoretical, worked in practice) -- get the adults involved. Make sure that your kid feels it's OK to tell you that he's been bullied (he's not being a snitch, he's bringing the problems to the knowledge of the right people). Then talk to the kid. Talk to the kid's parents. Make sure that if it doesn't stop, you will escalate -- you will talk to the school principal and the teachers. Make sure that the principal understand that you're willing to escalate further -- that you will make sure that it hits the local newspaper, that you will complain about it in the PTA meeting, and that you will be filing charges with the police for "assault".

When kids realize that there are consequences for bullying, and that they have to stop, they will. (The above goes for physical abuse, mostly. The solution for verbal abuse is "learn to insult them better". They either learn to stop insulting you, or they fall back to physical abuse, in which case, see above.)

That's what my parents did when I was bullied in middle school. They called the other kid's parents, and he stopped. There was one time they did need to threaten the principal with calling the police, and she pleaded with them not do it, promising that the kid was getting psychological help for his issues, and they agreed to conditionally back off (and he never threatened me again).

Bullying is already socially unacceptable -- it's against the law of society. We can solve it the same way we solve every other criminal activity, which is by involving the law enforcement authority.

Edit: Changed "socially acceptable" in the last paragraph to say "socially unacceptable" (was a typo).