How should I help my friend who is getting bullied.

[GdaTyler]

Try to avoid them. It's the right thing to report these assholes, but half of the time nobody does shit. I've been a victim of bullying where I was choked once, people threw my food down, hit me in the back of my head you name it, and teachers would have no guts to intervene. Parent arguments can get nasty as they usually won't amount to anything good.
In the long run encourage him emotionally and to get good grades in school and he'll do well and leave them to bite the dust. The majority of these cowardly bully assholes will just end up with shitty jobs and lives as it should be, at least I hope so.