Be Very careful about his age and body.
When I was 12-14 yo I was doing strength training and ended up having 3 hernia opperations overall.
He's body might not be ready for it so be very careful that he starts small and allows his body to adapt.
I didn't and ended up with having 3 ops (and balls like melons
).
Just make sure he takes his time, gives himself good recovery periods and doesn't rush into it.
