I'm late to this discussion, too.
PART of why we homeschool DID have to do with social skills and self-esteem--including bullying.
Someone said to "get involved" in the school to make it stop, but when you're fighting the tide--that doesn't help. If you're surrounded by other parents with the same mindset as DandelionKid--that it's a necessary part of the process and that this is why they're IN school: to learn how to handle and navigate these situations... and when some of the people of that mindset are the teachers and administrators, then really--what do you do? And that's been my experience more often than not.
My son had a spectrum diagnosis and when it was lifted, he was flagged for re-evaluation for Asperger's when he turns 8yo (which is when they're supposed to dx--not earlier. I know some Drs. do). He didn't (and still has a hard time) picking up social signals that would alert most kids to back off. As a result he's prone to being manipulated and bullied.
I am no more of the mindset that he needs to experience this to learn than I am in agreement with cry-it-out to learn self-soothing/sleeping skills or spanking for discipline.
He is still "prey" to the trends of the time with kids his age. Despite the lack of TV, he knows about (and has) Pokeman, Bakugan, etc. because that's what his friends have. Even among homeschoolers, values differ wildly. But he is not forced to focus his attention on managing around difficult situations at the expense of his academics and building the social skills that people love to think you get out of a brick-and-mortar school because he is too afraid to participate in them based on the reactions of a bully (in any form that you choose to define it--and that includes teachers sometimes... sad, but true--I've worked with them, witnessed them and reported them).
We pulled my son out of the classroom for his Pre-K year (he was mild special needs and had been in a classroom/daycare environment since he was young--full-time the year before Pre-K). He had gone to three different types of schools--all private. One was Montessori. I think the worst of the problems were sometimes notsomuch the other kids, but once it was the situation and the way the teacher was perceiving the issues and handling them (with the best intentions) vs. how it was affecting my son (which she didn't realize because she misconstrued his reactions, etc.).
As a homeschooling family, my son is not sheltered. He is supervised. By me. That means that I understand when he's in trouble because I know him better than his teacher (who may know them well by the end of the year--MAYBE--but that leaves a long span of time without that "knowing"). And I can pretty well guarantee you that I can supervise him far better than people whose time and attention is split among 12-30 other children (more if they're at recess). That means that when the kid on the playground (during afterschool hours--when there are also ps kids) goes to punch him because he's not really "getting" that the kid doesn't like him, yeah--I can step in (because I also don't believe he's going to learn anything through violence). That means that when he's really suffering from how he's been treated, I can help him replay the situation with accuracy because I witnessed it--where his teacher may have missed the whole thing and my son may have (or likely) missed cues/actions or misunderstood things and I wouldn't get the complete story if I'd not been there. That also means that I can help him process his feelings and walk through the "what ifs" for next time so that he has better odds of it not happening again.
No question, we have our share of troubles. In July we moved to a block where there are seriously no less than 13 kids that all play together. THIRTEEN. And we have some serious issues with 2 of them. One of which includes physical aggression. They are all public schooled. So really, there's not much in avoiding it. And unlike most (but not all) homeschool events/activities, I'm not always witnessing it. But he's turning 7yo now and I've had 2-1/2 years to mold him and direct him--so it's better.