First thing, (if I only knew then what I know now
) the worst thing you can do is make this a life and death situation for yourself. It is really scary, to risk rejection. I think in HS, we are looking to get help with our self esteem, and if you don't think that the case, then you wouldn't be worried about rejection.
The best you can probably hope for at this young age is to get an education from this young lady in the processes of the female mind. Talk to her. Ask about what she likes to do, music, TV, movies, etc. And listen to her answers. Don't be aggressive, my experience is that it is usually the female that engages the male, and they have this way of making the male think he has done the engaging.
In other words, you go halfway, strike up a conversation, then wait for her to come halfway. She will if it is what she wants. Take it slowly and don't push. It seems you want a date, but have you even talked to her? Don't put the cart before the horse, as they say.
I was lucky enough to work with several attractive young ladies at my job and got a crush on two of them when I was in HS. Girls at this age are usually (not always) more mature than boys. I got to know the two young ladies, never really dated them, although we went together to some functions. I was lucky in that one of them told me what I was doing wrong, and I listened. It did help me to understand how they perceived boys. Mostly, if you come on too strong, they get scared. Not only are they unexperienced like you, they also don't usually have high self esteem either. They wonder what is wrong with someone who goes crazy over them, because they don't see themselves as anything worth going crazy over. We are our own worst critics and especially at this age.
Anyway, you will find all this out on your own. It is like learning to walk, you have to fall down a few times.