Personally, I never found the door closed. My mother didn't either (she was a math/science nerd in a private girls' school, but the school helped her pursue her interests). I also don't see people closing doors for my kids based on gender, but if I do, I'll be sure to give them a good talking to
But I also would hate to see a generation of girls pushed towards engineering and math if they're not really interested. To me, it's like trying out veggies. I tell my kids that they have to eat a bite. If they don't like it, then they don't have to have more. Offer, but let them decide.
What I do see, though, is people closing off math options to gifted kids. That's the only thing I've seen, and it's not a girl/guy thing. It's an age thing. Drives me nuts. It's ok to be a piano virtuoso at age 14, but you (and your parents) are treated with suspicion if you want to take Calculus at 14. You can be reading Harry Potter in 2nd grade and they say "Oh, she's such a good reader, isn't it great that she's reading Harry Potter", but if your kid is doing 5th grade math in 2nd grade, "We don't believe in accelerating kids in math--they may look ahead but they don't really know what they're doing." I get that teachers think every parent thinks highly of their kids, but statistically, you're going to get one of those kids once in a while, so keep an open mind!