I have read that the Cogat is for initial screening only, and to use it as the only testing available seems unlikely - I would strongly suggest you find out more from your district/county.
At the very least they might allow you to submit testing that you seek for your ds on your own. If the teachers think there is a way to protest/reapply then there probably is.
I have also read that it is not uncommon for gifted kids to blow these sorts of tests - perfectionism, boredom, etc. do play a part.
We are in another area of the country, but in a similar boat. The county here does have alternative individual tests they can do upon request/with sufficient reason to think the cogat scores are not representative of a child's full potential.
You might have already found this thread..
http://giftedissues.davidsongifted.org/BB/ubbthreads.php/topics/37118/Test_Scores#Post37118I would also suggest the link found in this thread and just generally reading on this forum for more info on identification, testing, etc. Good luck!
http://giftedissues.davidsongifted....newest_guest_author_for_my_sit#Post37354