While I applaud JLAP for having the right attitude, I think things are just a bit different among school kids. They mercilessly abuse the designated "victim" for any perceive weakness. And the unwillingness to fight back is the biggest perceived weakness of all. In the adult world, JLAP is exactly right; fighting is never right, and can be extremely dangerous, plus adults are more empowered to take other actions than kids. Also, in the adult world, I've never found myself in a situation where someone is physically threatening me, except maybe in a hockey game or a drunk guy in a bar, but those are entirely different contexts where it's easy to avoid violence.
At some point, if it gets out of hand and no other methods are effective (including making the school take action), then fighting back is acceptable. Again, nobody should have to endure abuse day after day after day. That is what's truly unacceptable.
Use your judgement, Dino, and do what you have to do. Just make sure you've really exhausted all other options before fighting, but do not allow yourself to be hit. I wouldn't. I remember some of the abuse heaped upon some people in school, and I can't imagine that they came out of the experience without being permanently damaged.
Best of luck, Dino. Just consider that these days will pass, and the people who are "different" in school end up being the ones who are successful as adults, and the bullies who seem to control the school tend to end up being the total losers in real life.