Step up and let her know that you are interested. Most girls want a guy who is confidant. I wouldn't give any excuses for why you want to talk to her or whatever... Just be straight forward and speak your mind. Ask for her number and say that you might call her some time. If she is shy, she probably needs someone right up there in her face. I would not be shy back. Show her who you are and if you get rejected, It's her loss and it wasn't meant to be... But get her number before school is over!

Think of something cool & simple to do together, and ask her to join you. Don't be vague. Ask her to hang & talk about music or whatever. Once you get her talking, then you can get the number.