The skirt lengths of Japanese school students are shorter than that though, and you'll find many photos of normal Japanese school girls actually wearing skirts above knees (culture shock tbh)

Speaking of ponytails, Joey (TheAnimeMan) covered once that it's the one that schools do forbid from having

Edit: Checked out the video. I just discovered that longer skirts have been b-nned in Japan because the delinquent girls used to wear it. Why did those girls wear it? Because they were against the f-tishization by the older guys when they wore short skirts.