Unfortunately bullies usually have a group around them that they are trying to impress. This group is often the real problem.
So how does your son deal with this as a victim...as a spectator...or even the bully?
Tough questions because none of us want to think of our son as someone able to bully or to provoke bullying. But it must happen because they are always there.
As a Victim; what tools can you suggest to your son? Consider giving them a series of "tools" and label them that way for your son.
1. Avoid: Try to avoid the situation
2. Redirect: Redirect the bullies attention to something else such as playing ball etc.
3. Encourage: Statements such as "be cool man" toward a bully or "man you're going to be tough in football this year" are statements building the self confidence that is making the bully try to prove himself.
Every situation is different but you have to start somewhere. Doing nothing keeps the bully on track which always escalates the situation.
As a Spectator : Teaching a principle early on that watching the crime is just as guilty as doing it could change our world. There are plenty of bully situations that we allow. Case in point is a very popular TV series NCIS where the "newby" is constantly insulted and degraded. This is bullying but the characters in the cast including the boss do nothing to stop it. Great situation to point out to your son and ask, "would you like me to allow people to do that to you everyday?" All the co-workers would have to do is simply say, "that is way un-cool, why do you bully him like that?" This is all your son is responsible to do as a spectator. Remember the bully wants to elevate themselves so if the behavior lowers them it starts to reverse.
As a Bully: In the above NCIS example the character doing the bullying would never consider himself a bully. This is how all bullies see themselves. So defining bullying with your son is very important.
The Bible narrows it down to "Do unto others as you would have them do to you." Pretty simple rule that could stop all bullying.
No matter what your thoughts on the subject are...you need to discuss it with your son!