Exactly why can't he see through it well? Is it the clarity, the focus...? Could it be as easy as not having the corect eye relief for him? With the same scope off the gun have him move it so that it gives him the best view and see waht that distance is so you can mount it at that same distance. As a young shooter he may not completely understand what he's really wanting as far as the view.
Personally, I feel that one should learn with iron sights before moving on to optics so if he's a brand new shooter maybe start there.
Regardless, good luck and stress the safety aspects!