I have total sympathy for you.
I'm an adult with ADD -- not ADHD. I was always pretty much a straight-A student, when I was interested. It wasn't a lack of capability of learning in the other classes, more like a lack of caring. I could make myself focus when I say a point to it. Well, I say that, I could sort of make myself focus, to an extent.
The thing is, I was one of those, "she's a great kid, but she talks too much" girls. Good grades, so they ignored, or wouldn't listen when I tried to explain what was up in my head.
When I went to college the first time I struggled. I left.
I'm back in now and holding a 4.0. It's harder than h*ll. I also freely admit that I am medicated now -- I take Provigil.
The way I explain my thoughts to people -- think Dumbledore in the HP movies. The bowl with his memories in it - the pensieve.
In a way, that's how the thoughts get in my head. There are tons of things floating around, not really separated from one another. A lot there, just spinning. The Provigil gives me the ability to pull one thought out and complete it.
I agree that in boys, it's overdiagnosed, but I also believe that girls are often ignored if they have issues with the same disorder.
I wouldn't dream of special ed though. I know at the University I could apply for special stuff (extended test taking etc etc) but I won't. I want to earn my degree fair and square, and not something that is modified.