Is it normal to judge someones gender on the length of their hair?

Even kids do it. One time when I was younger I had shorter hair and this douchy little brat did that whole "are you a boy or a girl" thing. Some kids need to be smacked :/ I don't think hair length determines gender. I do however, feel like there isn't a whole lot that seperates males and females in appearance (Sometimes.) So it can be a little hard to differentiate if they aren't making an effort to expose their more "feminine" traits