Almost every handgun I have ever fired initially shot high. It is just the way I let a gun recoil.
If he is shooting consistent groups but they are just low what I would do is either install adjustable sights (this is what I prefer) or get a lower front sight or taller rear.
I dislike having a gun that I need to take a weird sight picture, I prefer to modify the sights to where I can take a more normal picture.
This may not have helped but fixing sights is usually not a hard project and very rewarding to say "I did that myself!"
My posts are things I have tried or experienced. You may or may not wish to emulate them so read them with this in mind.
Compromise means that both sides give something, but they never give, they just take.
I'm The NRA!