i dunno about you guys but when i was in hs there were 2 formal dances and 2 informal. i had the pleasure of going to each and everyone in hs. they were so much fun
at my hs it was
1) Homecoming
..............formal, in sense of a nice shirt, tie, nice slacks and the guy pays for all of it and guy asks the girl
2) Sadies (which is what i had or som schools call it MORP which is PROM backwards)
..............informal, jeans, funny outfits, etc, usually couples went as a themed pair. whether cowboys, identical shirts, togas lol whatever. the gitl pays for everything and has to ask the guy for a date
3) Winter Ball
.........semiformal/formal. i usually wore the same type of outfit as for homecoming. just a nice collared shirt with tie and nice slacks. girl pays for everything and once again asks the guy for a date
4) Prom
...........formal. as in a tux. guy asks the girl to go and pays for everything. then theres afterprom which is what i enjoyed alot too. for our school consists of going to a club and playing trivia, casino games (fake money) food, raffles etc
However, for all the dances except sadies and maybe winter, the guy gets the girl a corsage. this HAS to match her dress so ask her what color she is wearing
Also, in my exerience it is fun to go with a group of friends and go out to eat before the dance. For the formal dances make it be a nice upscale place. For informal, we did like chucky cheese or whatever
Remember to have fun. The slow dances are where it's at. Most of the time its just you and your friends danceing to up tempo/hip hop songs. but once the slow songs come on its all you and your girl.
Best of luck man! Hope I helped