The few times I was bullied was always the first few weeks after I arrived, and they quickly found out I would fight back pretty aggressively. Was that a "being poor" thing? Was it my notorious "punched a kid in the face for cutting in front of me in line when I was five" temper? Was it simply because I wasn't an "easy" mark?
I can't rightfully say, but one of those things definitely reduced my propensity for being the target of bullies.
The physical pain wasn't even the worst of it. What hurts the most 20 years later is the fact that I stood there and did nothing. I'd have rather had memories of losing fights than having never fought at all.
And honestly, getting kicked around by a full-grown adult at home was worse than anything another sixth grader could have dished out. I really don't know what I was so afraid of back then.
It was only when I got completely fed up with it / gained the courage to well and truly fuck up the people that were bullying me... that they mostly stopped. I'd been learning martial arts for some years by then, which definitely helped.