I have 2 DYS, one DD and one DS. I will say, off-the-bat, that male social relationships seem infinitely easier than female relationships.
madeinuk, I wish that you lived closer, because my DD10 really likes your DD.
I was as shocked as you are, though, when the ELA G&T classes were formed in DD's 3rd grade...and DD was a girl among many, many boys in the class! Actually, I figured with an ELA class, the bias might actually be tipped in favor the girls (I knew of more girl early readers, it seemed, than boys). Students were selected for the class, however, based upon a slew of tests. The tests included IQ, CogAT, Iowa, and MAP (among other factors). Apparently, boys did much better than girls on these tests (as DD was one of the only girls).
In advanced math class, which is EXTREMELY boy-heavy (and I DON'T think that they should let in girls just to even it out!), DD is typically paired with boys in group-work.
One of the reasons we went ahead and had DD fully IQ tested at the age of 8 (rather than waiting) was that we'd heard that girls can start to "hide" if testing is done later. Seeing the social pressures that have already started, I am very glad that we had testing done when we did.
DD has always been EXTREMELY independent and self-directed. She is not particularly susceptible to social pressure (so far). I can easily see a more sensitive female feeling the pressure to "dumb-down" and pretend to be interested in things that she is not. So far, DD doesn't seem to even attempt to fake being interested in things that she is not...which has a downside. She has always had, as HK astutely points out, more androgynous traits/interests. Until recently, she also spent a fair amount of time with boys (seems we've hit an age where that is getting more complicated...). Still, DD's personality DEFINITELY places her at risk for being labeled "too assertive," or other unpleasant things (sigh).
I think that HK's assessment is spot on. I do not believe that there are truly more HG+ boys than girls. I do wonder a bit about the tests themselves that identify, but I think that the bigger factor is probably social pressure on girls.
Luckily, DD has a very large class at school and she seems to have found her "people." We are bracing ourselves for middle school.
