A NeuroPsych Assessment (NPA) can be very worthwhile, especially if done by a competent NeuroPsychologist (NP). Some NP's have some biases against concussion causing prolonged symptoms. But, an NPA will give you good information about his capabilities.

At his age, understanding those capabilities is important, especially if he is preparing to go to college. Developing a plan for college entrance exams will be paramount.

I was totally unprepared for my SAT's and especially the PSAT that is used for Merit Scholarships.

Go ahead and support him in his efforts tomorrow. Expect that he may be exhausted after them.

My best to you.