I do know this, Tom House's work outs consist of weighted balls, however, he NEVER has the pitchers throw them. They are more or less used as weights to strengthen the shoulder. I'm okay with that aspect because a pitcher is simply getting weight training in the form of holding a baseball. Now, as far as throwing a weighted ball, refer back to my first post...
The weighted ball program developed by the National Pitching Association, i.e. Tom House and James Evans does include throwing weighted balls. My son did the program this past year. He had some increase in velocity but nothing more than what I think he would have had from just getting a year older.
Ok, have your son stop throwing weighted balls immediately! This is not part of Tom House' workout system. Like I said, House uses weighted balls, medicine balls, wonderweight, etc... I have never seen or heard of his program actually having the pitchers throw the weighted balls. Would you have your kid throw a shot put like a baseball? I truly hope not. It will tear his shoulder up. Granted, some weighted balls are a few ounces lighted than shot puts, but can create the same damage. Please do more research and if you do find ANYWHERE where Tom House has his players throw the ball, post back on this thread...