Go4 I am with you with respect to the question. It depends on the years and classes coming through. Our MS team right now has a mix, our other two middle schools have some talented girls that play summer ball. Our 2009 HS class, which went though the middle school two and three years ago were 24-1 over two years school ball, were our travel team in the summer at that age and won a few tournaments over that summer. Unfortunately, that talent got split between two HighSchools, but it does spread the wealth of skill I guess you could say. There are quite a few sophomores in that class, starting varsity for both schools right now.
Playing for their school at any age gives them a sense of Pride, Commitment and Team regardless of skillset. At this age, there is a disparity of maturity in physical size as well. We played a team yesterday with girls my height and we have a few girls pushing 5' if they are on a ladder. It all balances out at some point though.