In the above photo sequence, put your son in the position on the left, doing tee work 1st, then soft toss. In that position, he should punch back toward the Catcher and in one motion turn his belly button to the ball using his abs, glutes and legs until he reaches position three. The tee should be set in the middle of the plate approx. 6" in front of the front hip in position 1. The first movement with the hands from position 1 should be to point the knob at the ball and then swing as he would normally.
This is ONLY A DRILL to get the hitter to feel where the hands actually start to take the sweetspot to the ball. The reason a hitter gets outside the ball is because they start the top hand too soon to the ball and do not get the hips started soon enough.
Note the position of the bat shaft in photo 3. Your sons bathead at this point is more than likely almost even with his hands.