There is no downside to the kid staying at Bristol.
Kids racing to prep schools is normally much more about the adults who make money off the game than it is about the kids playing it. He already plays AAU ball at the top level - he doesn’t need more basketball, more travel and more wear and tear.
He’s a seven-foot sophomore who is on track to touch and go to the NBA after a year or two in college. Less is more for a 15 or 16 year old that size.
There is certainly potential for downside if he stays at BCHS. I'm shocked you have this take. He is practicing and playing against less talented kids 4 months of the year. The coaching isn't as good. The practice rules are more stringent. Especially true if he stays with his mostly regional AAU team.
There's also downside of going prep. The wear and tear on young bodies being a big one. His dad not being able to see all of his games, and the lack of fans is also a downside.
It wouldn't be a difficult decision if there wasn't downside to both options.
He and his family need to weigh the benefits of staying at home vs going prep. It sounds like he's really attached to his home, so if he stays home, he'll need to create a strength training program and a plan for skills improvement to stay on track with his peers at the top of the 2022 rankings. I'd think any talented local strength coach and skills trainer would be happy to take him for the publicity alone.