Around 2005-2006 when I hadn't changed majors to computer science yet and was student teaching middle school, there were still things being said to girls like 'its just more natural for boys' from older teachers.
It just didn't let them build the resilience up to work through the 'hard' aspects of math.
But, really, I have seen the exact opposite. Girls are actively encouraged to participate in math and science from a very early age in a lot of our schools.
I don't have any numbers on hand, but there seems to a drastic change in middle school where girls stop being interested in math and science. So by the time they get to high school, it seems like the fight for their interest is already over.
This is just my experience from being in education for several years.