Go online, find one of those sites that deliver chocolate with, like, custom writing on them. On it, have them write "You're sweeter than chocolate. Wanna go out?" Use this 2 weeks to your advantage as delivery time. Then, give it to her and say "I forgot this part of your present". Then, on the back, have "This isn't the only bar going into your mouth, and it's not the only thing getting eaten" written on it. Drives b*tches crazy.
Rickerslade, smooth as F***
OK, now, you go up to her after school ( or whenever she's alone, private moments are the best ) buy flowers/chocolate and hide it behind your back.
Approach her and tell her: Look, I know this sounds crazy, but will you go out with me.... Then take out the flowers.
While on the date, don't be nervous if she's late, girls do make up and shizz. And don't be silent/hesitant with her, be open with her. And dont be cheap, get her flowers on the date and invite her to a good resturant or place.
And the golden tip: Always, like always expect denial. If she doesn't like you, get over her, find another.
And thats all I can really give you.
And dress neat, let your mom pick your outfit. She's s girl, so she knows what girls like. And put perfume on, get a haircut if needed ( you do all of the following steps in the case of acceptance )