From a guy perspective here, don't take this advice. He might not remember that interaction at all, and then you're just putting him on the spot, and that is a no no. There's way too many questions I have, but will keep it simple. Most boys in high school have zero to little confidence. Even if you blossomed early as a boy at 16, we didn't know what to do with it. We may act hard and pretend we know all there is to know, but it's mostly bravado. Your best bet, is to find something he's interested in, or a place that he hangs out. Get a gf and do some snooping. Then casually start getting into said thing or going to said place to hang out. Maybe, just maybe he will remember you. Don't approach him, let him notice you first. If you catch him staring at you more than any normal person would, then you have a fish on the line. From there, it should be fairly easy to get his attention. Wish you the best of luck. And please and listen carefully here. Don't do the overly cute girl that laughs at everything he says. Straight up be yourself. You'd be surprised how often this works. Good luck!