Agree with others. He has to keep in mind that his competitors will be taking reps every day and playing a full season of JV. Then, I would guess that many or most will also play summer ball.
He has to play ball. He has to get reps. And he has to gain ground on the others in terms of speed & agility. On top of that, it would likely be very helpful if he could find a mentor/instructor that will assure that all the work is done with proper mechanics and mental approach so that he is maximizing his efforts.
Many areas have Spring ball for those who did not make their HS programs, chose not to play with their HS programs or didn't have that option. He doesn't necessarily have to wait for summer ball.