Lori,
If people in your family have headaches and they've still gone on with their lives your son has already seen that modeled. If he's experienced headaches and gone on he's developing strategies to do it. Take it for whatever it is worth, but I don't think it serves your son well for you to focus on trying find research that shows headaches are bad for cognitive performance. If anything it could be sending the message that you don't have confidence he can move forward in his life because you are still focused on trying to prove his test results should have been higher.
I think you'd all get a lot further right now by focusing on his specific needs and how you can begin to learn to cope with his disabilities and advocate for himself. Look to the future and focus on taking the steps he needs to take right now in order to be successful in college and in life.
