I just remembered a funny story from Home Ec class in Elementary school. We were making sweatshirts and our teacher was giving us some pointers about tweaking the fit of the shirts from the instructions. She asked us "So when you are making a shirt for a girl or boy what differences should there be?" We were all like "huh?" but also of course being 13 thought it was incredibly funny that she asked us the difference between girls and boys. Then she said as if she had expected us to know "oh well girls on average have longer arms". That was news to me!