Welcome! Glad to have you here!
Generally speaking, group tests like the CogAT aren't as accurate as the individual tests (like the WISC and Stanford-Binet). However, I believe the problem with the group tests is that they tend to show kids as scoring *lower* than they do on other tests, not higher. I could be wrong, but I don't think I am. That says to me that you have one very bright child on your hands!
I certainly think that if you have a specific question to answer that wasn't adequately answered by the CogAT, like "Is this school going to be equipped to handle my child?" or "Should we grade skip?" or "Should we apply to the Davidson Young Sscholar Program?", then you should consider further testing. If you don't have specific questions and the school seems responsive to the information gleaned from the CogAT, then you may not need to bother with more testing.
(Also, you should probably note that the CogAT is not one of the tests that DYS accepts on their application, so if you want to apply, you will definitely need to administer an individual test.)
I think you have to wait until age 6 to administer either the WISC or the SB. You're right that you could give your DD the WPPSI now, but unless you need the scores for school, I'd recommend waiting and administering the WISC (since she's verbal) once she turns 6 because of the ceiling issues. That means the WPPSI might not tell you what you want to know and might not give your DD the scores she needs to get into DYS, even though it sounds like she's probably a good candidate.
My only concern about the skip based on what you've told us would be the 2nd grade math. If she's coming in average at 2nd grade level, math could fast become an area of frustration for her. However, I think if I were in your shoes, I'd take the skip and do a little math work with DD over the summer to be sure she's ready. Assuming you don't think her social skills are a problem, and assuming she's happy with the idea of the skip, then I wouldn't look that gift horse in the mouth. I'd also start planning playdates with the older kids ASAP.
And to answer your final question, yes, you're probably in GT denial, but you might as well join the club!
I think the majority of us here are in some form of GT denial or another! The big things to decide are 1) what question are you really asking, and 2) do you really need another test in order to answer it?
I don't know that you need more testing to know that she's going to be bored silly in 1st grade, do you, really?
But then again, when faced with a similar situation, I had my DS tested because his achievement test scores were *so* much higher than I expected them to be. It's like I needed a tie-breaker test to show me that it wasn't a fluke! So it's very easy for me to say, "you don't need to test," when I needed it myself!
Welcome to the journey! It's quite a ride!
