Yea some girls buy expensive underwear just to flaunt them in front of their friends.. No I don't though because in my school we didn't have dorms so I never had to take off my clothes . However, when I go to the gym .. I prefer to change behind a curtain or something , I don't like people staring at my body..
That thought never really crossed my mind back when I was in high school. I never planned for it ahead of time. I would imagine its the same as a guys locker room. It depends on the girl, but most including myself just changed openly
It's been years since I was in gym class back in high school but I don't remember ever wearing fancy underwear for that. Mostly it was because I don't own any particularly BAD underwear so even my regular ones are OK looking.
As to what happens inside a locker room, it really depends where you are but we used to just change in the open. It's not like everyone walks around naked. You really are in your underwear for like one minute or something so there's no need to hide behind a towel.
I haven't changed in a high school locker room for 4 years, but I never really thought about the underwear I was wearing. We all just got dressed. Nobody ever took of their bra or underwear. It wasn't a big deal at all.
I'm guessing it like a guys locker room, we don't take off our boxers in front of anyone unless were taking a shower/ Need to change to a full sport outfit. So I'm guessing they do towel up if the twins have to come out. What goes on inside the locker room gossip and just friends talking most likely.