Take him to the cage or the field and make him hit everything and I mean everything to the backside. Tell him to be late.
Bounce the ball to the plate. Bounce it where it will come up late and he will have to wait for it to come up to hit it. This will make him have to wait in order to hit it. He will fail miserably if he is early.
Teach him that if he doesnt learn now to track the baseball deep he will continue to struggle against all levels of pitching but especially better pitchers the longer he plays.
Another drill is the ladder drill. Stand on a ladder and place a plate down under the ladder. Drop the baseball down and tell him he can not swing until the ball gets below his waist. He will have to wait on the baseball. He will struggle with this drill but it will help him.
Backside toss. Get behind him and toss the baseball soft toss to his back thigh. He has to hit the baseball backside. Get him to think "see the baseball deep" "let the baseball get deep" "see the baseball and think deep in the zone"
On the bounce drill bounce it close to the plate where the ball comes up really late and he has to wait and see it really deep. Slow down the bp. Throw him cream puffs and force him to have to wait a long time to swing. Then gas him from a close distance. I mean gas him from really close. Then mix him up. Force him to learn how to hit and not hack.
He is jumping the ball and not truly hitting. He is predetermining his swing and he has no timing working. Some kids learn this by being thrown the same speed bp over and over and over again. Hitting off t's constantly and getting the same speed bp over and over again.
Good luck