How important is this? Because at this point, he’s probably going to benefit most from some private tutoring.
Is he looking for a high score in order to get scholarship money? Or are you full pay? He already has a very high score. A private tutor is his best shot at figuring out where he is messing up, because he is literally just looking for a point or two in each section to bump him to the next level.
It’s very difficult for kids with already high scores to do even better. I’m linking the pinned post on this forum. It’s very possible that at this point, he is making some fixable mistakes that might just get him the points he needs. Common sense tips to help raise your SAT/ACT score