My department hosted a group of 40+ high school philosophy students yesterday (the high school is a public high school in a lower-middle class part of town). They were attending a couple of introductory classes and checking out the university. I would say that more than half the kids were girls, and all the ones who asked questions were girls. And they asked smart questions. It was great in oh so many ways.
As a side note: The department is developing a strategy to work more closely with high schools who are teaching philosophy, or have philosophy clubs. Interestingly, it is the grad students who are the force behind this.