The rates seem to vary by location. We went with a Hoagie's list tester - with vast GT experience - for our two DYS. We had two excellent testing experiences and the scores have helped our DC access some G&T resources, including DYS. We are very glad that we went ahead and did the testing (we thought about doing it for years).
I guess that the caution that I would provide is that even WITH proof of DYS-level scores, there is no guarantee that your school will do ANYTHING additional with your DC. Your state laws may help you...or they may not. Your best bet is to be aware of your state laws, local school policies, etc. and test with these in mind. I would definitely use testing that is most likely to be recognized by your school (some schools summarily reject outside testing).
I hate to paint a bleak picture, but we've slowly realized that meeting our children's needs is pretty much up to us (we are getting little or no additional help from the school - we do NOT live in a state with great G&T laws).
