Are Han and DK in high school?

So they are either in high school themselves, or they spend a LOT of time hanging out with highschoolers. I can't figure out which makes more sense based on what we see. Han and DK both have business with the Yakuza, have multiple expensive decked out cars, and were played by actors in their 30's. Everything points to them being long graduated, but then why are they dating highschoolers and hanging out with them so much?