It's normal but it shouldn't be. It's not your problem though, because they'll be the ones getting unwanted attention. I think it looks terrible also and trashy, but if they think it's cute for whatever reason, then who can stop them. It doesn't make you a prude to cover up your butt, it makes you a regular modest person who knows how to dress.
Yes, It is normal. Almost every girl these days does it. -sigh-
Yup a lot of girls do it, kind of sad
I hope it's not normal! And I'm surprised that your school doesn't have a dress code to prevent it. I think it looks trashy.
In the 1970s and early 1980s, these were called Dolphin shorts.