P.S. Testing is usually performed by psychologists. You can ask your school to refer you to someone--though you probably want to be sure that the person you choose has experience with testing GT kids and not just with testing kids for LDs. If you want to get a better idea of the extent of your child's abilities through the testing, then you need a tester who doesn't stop the test too early.
Hoagies has a list of experienced GT testers, and snowgirl linked you to it.
Some university psych departments offer testing for less $$$, but again, you want to be sure you're getting what you want/need from them. Inexperienced testers might not know how to get the fullest responses from a GT child, so you might not wind up learning very much.
