I was like your kid. Finally figured out that "girly" gifts that I'd taken offense to in middle school were from genuinely nice classmates that enjoyed dressing up and stuff from bath and body works and had assumed I didn't have the option to get girly stuff at home. Not the case- I just didn't care to shop and my mom wasn't the kind of person to buy me stuff without me asking for it. And strong odors gave me headaches so I hated bath and body works.(I mean, I'm not saying it wasn't a power play in your kid's case. It just isn't always.)
Sure, part of it was body image. But most of it is that I didn't know how to shop and didn't really care to learn.
I'm not saying that uniforms don't make a difference. But the worst of the bullies pick likely targets and then hit them at their weak spot. Clothes are just one thing that make a kid a target. If you stop reacting to jibes about your clothing, the mean kids start on something totally different- your hair color, height, hobbies, grades, what you did over the summer.
So I don't necessarily agree that uniforms really solve a bullying problem. It might reduce the visible divisions. But that doesn't mean kids aren't still being bullied. You dress kids exactly alike, hair styled exactly the same- they still can tell you who the insiders and outsiders are. They know who the targets are. The power dynamic and insecurities are NOT reduced or removed.
Oh, I don't think uniforms solve bullying at all. I just think they can be a small part of an overall strategy to reduce social aggression and encourage a sense of community and belonging.
Bullying has to be fought from multiple angles.
1. On the home front - it starts with not being a bully yourself. Don't use your superior power to coerce or control or humiliate your child. Teach your child that they matter as a person, that their opinions matter, and that they are respected, even when they can't always get their way.
2. In schools - respect your students. Listen to them. Avoid zero tolerance policies, and treat your young people as individuals. Teach students to identify bullying and empower them to stand up to it.
3. In school administration - give teachers a voice. Give them a reasonable level of autonomy in their own classrooms. Avoid legalistic policies that do more harm than good.
Essentially, the only way to combat bullying is by encouraging respect on all levels and community-building.
My local (edit: public) schools actually did a great job of teaching kids where the line is, and how to appropriate react - as a group! - to incidents of bullying.
A perfect example would be when my daughter got into a argument with another girl, in her high school locker room. She was in grade 9, as was the other girl, but due to the way the classes were organized the other girls in the room were older. Note - my daughter was born with a large birthmark on her upper lip, and wasn't entirely done with her surgeries at this point, so she looked a bit different.
The girls bickered back and forth for a bit, and eventually the other girl, frustrated that she was losing the logical argument, said, "Well... you're UGLY!"
Immediately, all the older girls who'd been ignoring the fight to this point, turned around en masse and said, "HEY! You can't SAY that to her!"
My daughter came home in an absolute state of astonishment, that people who didn't even know her would stand up for her. I give full credit to the years of training these kids have had, with regards to what's acceptable, and what isn't, and how you're expected to respond. (ie, nip it in the bud, before it escalates)
Back when I was in public school, all I would have done was think, "Thank God she's not saying I'm ugly!" And if I'd been the target, no one would have stood up for me. One of the reasons I applied for that private school scholarship, was because one of that school's girls (in uniform, which is how I knew what school she was from!) stood up for me when some of my schoolmates were harassing me on public transit. She wasn't even from my own school, and she still stood up and told them to go take a flying leap (in less nice words), because her family, her school, and her world had taught her she had a voice.