I haven't read this entire thread, stopped on page four... Just thought I'd give my two cents worth on the original question.
I was "middle classed" all the way up until fourth grade. I went to a Catholic school, and their wasn't much fighting.
Once I moved to a different school in fourth grade, all hell broke loose. All the way until sixth grade I was teased to kingdom come. I just ignored it, because if you got hit (even if you didn't block, just got hit for no reason) then you got the same punishment as the person who hit you.
I got stronger during the first half of sixth grade (competitive swimming) so by the time I moved to my present location for the last half of sixth grade, I was able to defend myself. I got stronger still that summer, and now I am completely capable of picking on kids myself. It's the fact that I know what it's like that keeps me from it. Anybody that does want to mess with me gets punched (usually in the stomach or nads where it won't leave a mark to show the teachers).
So, I say, violence isn't always the answer. But I'd rather beat the **** outta somebody than be called a coward (I have to much pride, one of my weaker points), or wach my friends get hurt.
As for people mobbing you, fights in my school are usually well organized. If two people start fighting, everybody will stay back and let them have at it.
If somebody is going to fight you, and there's no way out, don't take it. Minimize your injuries by fighting back, and making lots of noise that will attract teachers that will break up the fight. It makes you less of a coward if the teachers break up hte fight before there is a clear winner. In most cases (at least at my school) if you show the courage the fight, making you more difficult prey, people will back off.

EDIT: Just remember, if they're bullying you, then you must have something they want. Which could be your intelligence, talents, or even a nifty briefcase so they can carry around all their books more easily,:D