I recall that when I was at high school in the '70s, when we had mandatory hockey we'd wear our navy blue pleated games skirts with a pair of navy blue shorts under them in order to make sure that everything was covered. (The PE uniform was actually supposed to be navy shorts or the games skirt plus navy blue knickers but - certainly one we reached S3 - about 14 yrs old - we all wore the shorts with the games skirt.)
I often have a problem getting trousers which fit comfortably - I'm between 5ft 8 and 9, but my legs are only 31 inches: it's my torso that's longer.
To the trouser equation, I'll add that girls tend to have more of a bleed-through problem with trousers than with skirts in my experience.
No, I'm not looking (before anyone starts commenting) but particularly when I was a young secondary school teacher I'd have girls coming to me for help when they were caught out. (More specifically, they'd send one of their pals to speak to me.)
At the point when I was in perimenopause, I recall that I more or less gave up on wearing trousers to work and switched to thick skirts. Even running to the loo at the end of each lesson left me in danger of being embarrassed - and that was with HRT. (Yes, I did see my doctor.) Possibly because of my own problems, I'm in favour of girls having a choice.
So far as problems with short skirts and unsuitable trousers and leggings are concerned, believe you me that it did become very obvious in the classroom.
I can't recall ever being aware of girls rolling up their skirts. I've only ever worked in Central Scotland.
The midi was in fashion when I was at high school and the girls round our way don't need to roll up their skirts - they just turn up in mini-skirts. Some kind of elasticated concoction appears to be in vogue at the moment, though they're wearing them with black tights.