Catching is not for everyone
He has to be mentally tough to catch.Chances are Coach will blame him for most things even if they arent his fault.
At the HS level,a catcher has to block the ball well.He cannot be sacred of the ball.Blocking in a way is a desire not a skill.
He has to be able to frame a pitch and not make it incrediply obvious.This usually works by breaking of the wrists versus moving the hand as a whole.
He has to be able to control the running game.Chances are if he wants to play varsity he needs to have a pop time to 2nd base of no more then 2.5sec(or most places have ideal times)
What would I reccomend?Have him go to the local HS or just any place that has pitchers for that matter and have him ask to work bullpens.He can work on all aspects of his game here and get used to catching game speeds.Throw him blocks 4 times a week if not more.Go 3 sets to the left,3 to the right,3 down the middle,10 throws in each set.Also Jump ropes to quicken his feet.
Aside from that have him read sites like this one we are on(see the catching section on the main page)and also read stuff like this and talk to guys like this.
http://www.brescia.edu/athletic/Project.htmI have personally talked to him and several other coaches(even some D-1)who can give helpful and supportive advice.
He needs to want this because its completely different from any other position.Good luck!