That might be a temporary fix but probably isn't the true answer.
It is quite possible that he has a long extended swing and the opponents coaches have figured out how to pitch him.Jam him and he may not be quick enough to get the bathead around to catch it out front.
There is a good chance that if he backs away from the plate,they will start to pitch him outside,this is assuming he is facing pitchers good enough to place their pitches like this.
Of course,this is all assumptions and without seeing him,no way to know for sure.
My bet is he needs a shorter,more compact swing.
BUT,there are way more qualified on this site than me.
I am just familiar with 2 kids in our 9-10 year old league that we pitch inside(or atleast try to) because they have extended arm swings and if they get extended on a ball,they will hit it over,so we jam them.