The more subtle your hints, the less likely he’s going to notice them. And even if he notices them, he might not elect to do anything about it.
You need to learn how to hook him. Look into his eyes a little longer than you ordinarily would. Touch him on the shoulder or arm when you’re trying to make a point. Ask him questions without yes or no answers and make him give you a real answer.
Ask him to do something for you. Doesn’t matter what it is. Maybe it’s to walk you to your class even if it’s out of his way. Boys are suckers for that kind of thing.
Don’t listen to these adults who say you should be upfront. That’s how adults do it because adults like confidence. Kids aren’t necessarily going to respond to that. I was absolutely terrified every time a girl showed interest in me when I was in school I was worried she was just trying to make fun of me. But if she did what I’m saying you should do, I would not have had any defenses against it.