(I just read he has a gf. Time for you to look elsewhere. He's not going to leave her for you.)
First, I'm a guy. Second, I was very shy in high school, so I know how you feel. Third, there are steps for getting to know someone, but it's not a "game" like some people say. Talk to him for a few days, then decide if you want to date him. Then, if he doesn't ask you out, YOU ask HIM out. This is not the 1950s. Girls can ask guys out.
Or you could say "So, when are you going to ask me out on a date?" If he doesn't get that obvious hint, move on. But give him a week to actually think about what you said, as he might not quite believe you. Be aware that if you say this, you come across as being "needy" by making him pay for everything. And you certainly don't want THAT reputation in high school. As guys will run away from needy girls.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)