OHSAA or whoever is in charge of recruiting (not too familiar with this) should be sending information/recruitment flyers to High Schools to pass to their senior athletes. Most of the athletes aren't moving on to play at the next level but may still want to be involved somehow. I don't recall anyone ever asking me to think about becoming an official while still HS/college aged. Granted this was 30+ years ago, but I and probably some of my teammates would have at least listened. I wasn't approached about officiating until I was in my 30's and working tables at wrestling meets/tournaments, but by then I was already attached to a school as a volunteer and didn't really have the time.
Also, I'm sure some schools would let an official or representative come into the school for a 30 min to hour long sell and Q&A session for interested students. I worked for the YMCA and many times I asked and was permitted time / space for similar talks about volunteering and other teen programs. May get a bunch of kids who just want out of class, but if you can get a couple of solid commits, I think it'd be worth the time.