Willj, your son needs to learn technique such as rotating into foot plant.....Weight shift momentum is something he needs to learn and understand, also....
He is probably keeping his weight on his backside....And, counter-rotating his shoulders is an improper loading process.....
Itsinthegame has given you good advice about learning how to load properly and about being careful who you choose to teach your son.........Hitting is about loading and unloading in an efficient manner....It's about moving the body properly....
I really would suggest you get in touch with Steve.....He can help you....