Drama like Boys Over Flowers

Yeah, I know, you're ALREADY groaning..

I'm looking for a romance drama in a school setting where the female lead eventually has to pick between two main guys. (Woo Bin ♥) 

If you like Woo Bin then watch School 2013. I don't really remember there being romance in that one but there is definitely bromance which can sometimes (such as in this case) be better than the romance that forms from a love triangle. Main focus of the story is of two guy friends who had a bad falling out and how they try to reconcile with each other. 

Keeping with the Woo Bin theme, the movie Twenty is a great watch about 3 guy friends who try to find love and their path in life.

Another kdrama with a high school setting with a focus on music with some romance would be What's Up. Stars Daesung from Big Bang if that's your cup of tea. Plot focuses on a guy who tries to run from his criminal past by attending a preforming arts school, falls in love yada yada.

Sassy Go Go is another high school one with romance that doesn't focus on music but instead dance (choreographed hiphop). Plot is about a group who formed a dance team (who happen to be the the underachievers/low test scores) at school and how they butt heads with the study group (the smartest kids in school).

You're Beautiful isn't a high school one but it has the music aspect. A girl disguises herself as a boy to sign on with a kpop band. I actually didn't finish watching this one because of the love triangles but it seems that's what you're looking for :p

I second "Cheer Up!" (aka Sassy Go Go) it's one of the best school dramas I've seen. Also another I can think of that has the girl choosing between two guys is "School 2015: Who Are You" and "Reply 1997".

School 2015: Who Are You
Monstar
Sassy Go Go
Whirlwind Girl - Chinese martial arts drama, 3 guys fight for main girl.