Im 15 and in 10th grade and she in 9th but doesn't know I like her, we don't really talk but when I see her I want to ask her out but my doubt holds me back because we really don't know each other. Any ideas of what I should do?

Chicks really dig confidence! Just go up to her and ask. But that's really hard :-)
Or give her a flower (not a red rose because that's too much maybe yellow rose or a daisy) and just say "because I thought you needed a flower" or something like that. This will get you on her radar as a sweetheart, then you can move in slowly. Girls like guys who are willing to befriend them first and almost all of them like flowers! Good luck!

Start talking to her and see what happens don't just jump in head first get to no her abit

Introduce yourself, and get to know her by talking to her.

never ever ask a girl out if you don't really talk to her/ knowing her...

be friend ^^... have fun talking to her first then later on the road try to see if she likes you or not and also help you that to find out if you really likes her or not ^^