Hi and welcome to the Chiari forum.
As Frankie mentioned do make sure his teachers at school understand when he asks to go, that it could be a problem....so they do not tell him no,....'
and the link he provided is a list compiled by the members here,...it is not meant as a referral nor an endorsement of those listed on it, only that a member here was treated by, and liked the Dr....also not all NS's treat children so you will have to call and ask that as well....
Most of us do have to travel to get to a specialist that is right for us, so do look outside of TX if needed.....
I do have tether cord also. I have had the surgery. I am doing great. Just make sure since this age that the teachers know if he ask to go to let him. Far as headaches I usually take a Advil and they go away. I do have some that it might take to rounds to get them gone.
http://www.medhelp.org/tags/health_page/39830/neurological-disorders/DOCTORS-LIST-FOR-CHIARI-SYRINGOMYELIA?hp_id=1062