Correcting a bad throwing motion

Question
I have a young player who has developed a bad throwing motion.  When he throws the ball, it looks like he is throwing a javelin or a shotput.  When he rares back to throw, he brings the ball close to his head and pushes it out.  He is not extending and getting that sling-shot effect when he releases.  Do you know of any drills or excersises that would help him feel how his arm should be when he throws?  I've tried everything that I know of but he still brings his arm in like he is getting ready to throw a spear.  Any suggestions?

Answer
Have you thought about making him a football quarterback?  With that motion he probably throws a nice spiral.  Getting back to actually answering your question, throwing mechanics, fielding mechanics, hitting mechanics, any of them all tend to revert back to muscle memory.  That's why you see major leaguers hitting hundreds of balls off a tee day in day out.  Your youngster is making his mistake because of the same thing.  When his mind says throw, his muscle memory basically takes over and brings the ball straight up and pushes it.  To correct this you're actually going to have to fix 2 problems, the loading up prior to the throw and the follow through afterwards in order to give him a full range of motion on his throws and hence the "slingshot" effect you refer to.  Both can be fixed just by playing catch a few minutes each day with a slight modification.  Simply have put him in front of some sort of obstacle (a wall, backstop, whatever).  Mark a spot on the ground in front of the wall just far enough away that he can reach back to throw and touch the ball to the wall with his throwing arm slightly bent at the elbow.  Have him be on that mark each time he throws to you.  Each time he throws, have him reach back touch the wall with the ball and in one motion throw the ball.  After release, have him touch his stepping knee (left knee if he's right handed) with his hand (this will be impossible if he pushes the ball).  Have him do this each day for a while and it will gradually modify his natural throwing motion.  Just make sure that the entire throw from touching the wall to touching the knee is in one smooth motion.  If he does that, he won't be able to shotput the ball.  Hope this was helpful.

P.S. Be ready to chase some bad throws at first.  It's not going to be pretty with that drastic a change to his mechanics.