Was bullied exactly once as a kid, at a playground. Mother brought me back there the next day, told me to walk up and punch him in the face. Did it, we became best friends.

This is how humans work. There are a lot of comments here about how schools break down that sorta behaviour, and they might be right. But its also up to schools to teach kids how society works, so all that means is you have to tell your kid to punch the other kid, after school lets out. That's as much a societal lesson as standing up for yourself.