Just wanted to say that I haven't read all the posts here. From there....
First, I'm not sure how big "full-grown, adult-sized" boobs are. I'm 35 years old and am barely an A-cup. I've known 11yo girls who are waaaay more developed than I am.
Secondly, if anyone thinks that wearing a bra is going to ward off ill-mannered boys, you're dead wrong. Like I said, I'm small chested. No boy ever grabbed at my chest in school. But I can't tell you how many times a hand has found its way to my rear end. I'm rather shapely in that area.
If your daughter wears jeans, boys will be checking out her butt. If she wears a skirt, they'll be looking at her legs. And yes, if she has anything in the chest area, they'll be looking there, too.
But the idea that girls are responsible for a boy's hormones, sickens me. That's pretty close to saying that girls who dress in a certain way are "asking for it"..... or that a girl who wears a short skirt deserves to be raped, because she provoked the male.
Lastly, I don't think a teacher has any right to tell students what kind of underwear to put on, no matter how the student is built. As long as nothing is see-through and stuff isn't hanging out, that's all that should matter.