Just to elucidate on the original point a bit:
Successful (and even, to some extent, failed) resistance to violence, assuming it was justified) has a net benefit to all, as it imposes an increased cost (in the form of being beat up, or at least exerting extra effort or suffering some pain) on committing violent acts, thus discouraging them. This does not of course mean every specific, individual act of resistance has this effect (imagine I tried to fight off a bank robber but instead stumbled and fell over and broke my wrist - the bank robbers would laugh at me and maybe hurt me some more), but it is also wrong to say that resisting personally has no net public benefit.
I would agree, but there's a very different dynamic at play with bullying as opposed to robbing: when you're robbing someone, violence is incidental. You don't want it; you want the money with as little muss and fuss as possible. In physical bullying, the bully to some extent wants
the conflict: ideally a conflict with someone perceived as a beta, demonstrating the superiority of the bully. A meek surrender can still be used to mark status, but an actual fight is not a disincentive as long as you win.
But back to our point, how do we even begin to deal with psychological, group bullying?
I have moved from some truly bad schools to a very good school, where bullying was pretty much a non-factor, but I cannot tell you for the life of me how teachers prevented it - perhaps simply through being good, dedicated people. Anyone on the forum have experience with the more complex methods involved?
I believe one thing that needs to be done is reducing the distance between students and teachers, plus lightening of the workload on part of personnel. At most schools I've attended, teachers viewed bullying as disruptions of their already jam-packed schedule, so they tended to order said disruptions into two categories, issues that would work themselves out (i.e. regular physical intimidation and social ostracizing) and atypical behavior that requires correction (bullied kid snaps and fights back, skips classes, or is otherwise actively opposing this treatment). The easiest, less stressful way to discourage the latter is to blame the victim, so that becomes a temptation.
Also, of course, schools need to combat their own tendency to downplay bullying, whether social or physical, as either "a phase" or "boys will be boys"/"girls are like that".