How about Mercersburg? It’s no farther away from you than schools in CT or RI would be. It is in the MAPL league, meaning it competes against Lvillie, Peddie, Blair, Hun and others in your area. Strong learning center, not an athletic powerhouse (meaning a good (but not necessarily great) athlete can make significant contributions to our varsity teams), not a pressure cooker - everyone can find their passion and work at their pown pace, and a place that loves nice kids. We’ve got 440 of them! 
Good luck; I have no doubt he’ll find a successful place to land, as did sister.