Since I just had a graduate course that dealt a lot with this subject, I thought I'd chime in.
Tests such as the CogAT are group ability or aptitude tests. The testmakers will go to great lengths to distance themselves from IQ, but in reality IQ is the construct that it was designed to measure. In fact, it has over 80% validity measuring the construct of intelligence (concurrent validity when compared to the individual tests such as WISC), which is pretty good. That being said, 80% leaves for a lot of error, and I think the standard error of measurement is around 10 pts (don't quote me on that but I'm sure we could look it up).
There is rightly a lot of animosity for tests like the CogAT on this board, but this comes from its misuse. The CogAT is an extremely valuable test when it is used properly. First, it should be used as to screen the entire population of students. Again, don't quote me (it's amazing how soon this info disappears...) but I think the CogAT costs schools about 1/100th or maybe even 1/1000th of an individual WISC. The reason it should be used to screen is because it adds some objectivity to the question of who gets to go for the full testing. Mind you, teachers and parents should absolutely still be able to nominate students for testing as well. It simply helps to identify more truly gifted students (particularly in cases with poor school performance, little parent advocacy etc), and that's not a bad thing!
The second appropriate use of the CogAT is to gauge student performance compared to ability. Our district gives both the CogAT and the ITBS (achievement test) and develops reports that compare the two. If there is a great discrepancy between ability and achievement, that raises a red flag that perhaps something is wrong. Maybe the teacher is not getting through to the student, or maybe a learning disability is involved.
CogAT results should definitely not be used as a requirement for gifted services. I would be in favor of an either/or approach (maybe because DD7 is a high CogAT girl
) but not an all-of-the-above. CogAT is simply not as accurate as an individual IQ test, especially it seems for HG students. From many of your stories, it's obvious that some schools are misusing the CogAT as a gatekeeper test, and that is just a shame.
