Was the tester skilled at working with GT kids? If not, scores can be a fair bit lower just from that. If the tester is used to looking for learning problems but not high scores, s/he may stop asking questions too soon.
If your "mom gut" is telling you that the score is too low, then it might be a good idea to get a full IQ test from someone who is used to working with GT kids. If you need the 130 to get the help you think he needs, then I'd say retest. IMHO...
I don't know if you need the achievement testing. It was useful in our case, but if you would only have him take it because you're curious, I'm not sure it would be worth it. Unless the tester offered a 2-for-1 deal or something. Then I'd jump at it if I were you!
