Or I've been around the competitive running scene long enough to see a lot of people with regrets. "I should have run more in high school" or "I should have trained better."
If some guy running in the 19s for a 5K gets shin splints or plantar fasciatis and can't run for 2 months from training too hard, well frankly that's unfortunate but not a big deal. He'll survive, and he has the rest of his life to run road races. But in the unlikely chance that he takes to that training, and adapts well, then that's a potential life changer for him. All I'm saying is, let him try and figure it out. Running in HS is a competitive sport. Every runner needs the mental toughness and competitive fire to get anywhere with it.
I'm not saying he should go from 35mpw to 80mpw in the course of a single summer (although a good number of HS runners do make this leap and successfully go from zero to hero in a single season). Rather I am saying he shouldn't be overly cautious, scared of injury or act like going from 35mpw to 50mpw is a big deal, because it isn't. Increase pace and mileage carefully, but not too carefully. HS runners are chronically lacking in mental toughness - it takes courage for the OP to say, "screw it 60mpw is something I can do" and set a goal and actually get there. It takes commitment to run significantly more than his teammates are, and sacrifice to make being tired and hungry all the time a lifestyle choice. Everything and everyone around him is going to be telling him he's doing too much too soon, that he can't do it. Maybe OP doesn't have what it takes, or he simply is not interested in this path, and that's totally fine. But there are a thousand websites online that are telling him "10% rule", or "run your easy days EASY" or "you're running too fast!!!!". There needs to be a disclaimer (me) telling him, actually no, you need to train "harder, faster". Actually those same people who spout "easy easy slow" will tell elite runners, "these rules apply to the masses, not to you, you guys are different", so he can make an informed decision.
Also, everyone telling him to take it easy or that I am crazy, I guarantee you has never run D1 and probably never was that competitive in HS. Those of us that did know what it takes to get there, and know that road is very painful. None of us got to where we are by following the 10% rule or running 3 very easy days a week.