Most likely, he'll get much better with time. But he needs to rest so that he can get better. Maybe reduce his work load by enrolling him in regular classes, or enroll him in home school or independent study so he can do work when he feels like he's able to it at his own pace away from all the overwhelming stimulus schools are filled with. Or maybe it would be best if he were to get out of school completely until he's doing better and then he can reenroll when he feels like he can take honors classes again.

I also definitely recommend that he not play football anymore. People are more apt to getting head injuries after acquiring them previously and they have a compounding effect on the brain, so each one is worse regardless of the blow that caused it. Even shaking the head, whiplash, etc. can cause the brain to rattle around inside the skull enough to cause serious damage.

When I was in High School, I was in a lot of Honors Classes (our school was the magnate school for academics in the district.) One of my friends was in a very bad car accident and she had to withdraw from school altogether for over a year. She graduated "late". Now she's a very successful M.D. in San Francisco! She had to take the time she needed to heal before she could excel again and it didn't prevent her from fulfilling her potential.

Make sure he is taking all his vitamins and minerals daily, including a good B complex and Omega Oils (3-6-9) because those are especially important for brain health.

Much luck!