I don't wish to stir anything up here but I think it is about exposure (similar to what someone said about kitchen sets and female stay-at-home parents). For example, at my secondary school, boys did football, rugby and athletics in PE. Girls did netball, hockey and athletics. Guess what, I knew people from both genders that were good at athletics. Obviously, the physical composition is different, but if someone is exposed to something at a young age, it becomes more about drive; one of my friends (a girl) beat all of the boys at cross country, just as one example. At the end of the day, there are other factors that influence your decisions (inherited, environmental variation) and I know girls that now play high level football and rugby, but for the most part it is about exposure. Similar things with more academic subjects, I was not only taught to read at a young age, but I was taught to love to read. This is the one simple reason why I was one of the best writers in our year. If I did not have that exposure, then I would not have been at that level.
Moving on to the whole career thing, who cares if a room is full of mostly men or women? OK, maybe it might make the less confident of us a bit nervous, but that is down to societal pressure IMHO. They should not affect your learning, just as a member of your own gender shouldn't. There are no barriers to women, that are not there for men (one general reason is that it isn't 'cool' to like programming, so I spent my time 'watching TV' instead of playing PS3 when I was asked). That is the only thing that needs to change, STEM subjects should be taught to a fuller extent. I have attended many STEM events and they are much for interesting than a boring science 'experiment'. Again, exposure. If people 'try' STEM subjects, they might (or might not) like them, and pursue them as a hobby/career; same with other career paths, its not just STEM subjects.
But do not say that girls are disadvantaged. They have the same opportunities as boys, and face the same adversity. Just my two pence (english) and criticism and disagreement is welcome, so long as it is presented in the right way.