Everyone has already given really great advice so far, but I just want to touch on the topic of keeping home from school.

I suffered a concussion during my sophomore year of high school and had no accommodations. My school has since implemented a no-work policy under which students with concussions are exempt from all work while they are concussed and are only held responsible for major assessments (they make them up after they're healed). Looking back, I wish more than anything this policy was in place because the stress I was under for those 8+ weeks probably was a major contributing factor to my current condition (18+ months later). I was overstimulated, confused, disoriented, dealing with splitting headaches, etc. all while juggling eight classes and four hours of homework each night...if that's not a recipe for disaster, I don't know what is.

I suggest you check if your son's school has any such policy. I know my particular high school is very concussion-savy and that not all schools are, but you might find that your son's school could be accommodating as well. If they don't have any policy like this, I would definitely suggest keeping him home longer. Slowly begin to do the work at home and begin to work back up to full days of school until he's into the swing of things. It's better to take it slow and steady than to rush back into things. Again: recipe for disaster.

I hope his school is understanding of his situation. Mine wasn't when I was going through it, but now they are and a few of my friends have really benefited from accommodations made while they were recovering.