I'd say forget about what the rest of the school thinks, act confident, buy yourself some nice clothes, put on some hot makeup and strut your stuff girl.
Yeah getting the guy is about looking good, but it's also about FEELING good too.
My advice is try flirting with him a bit, but don't get too carried away. Then if he responds well, invite him to do something with you in private. Make sure it sounds totally innocent. Something like getting food together or watching a film. If he agrees and wants to spend time with you, then this is a sign he likes you.
If he's not into you, then he might say no. That's ok though, because you can ask someone else to hang out instead. That will take the pressure everyone assuming you like him, because then you can argue back "no, I was just bored and wanted to hangout. If I like him, how comes I asked someone else to hangout instead?"
Then when they don't know what to say, you hit them with the line "God, you guys are so immature". It's a killer. No-one will mess with you.
