Personally, I think that the group tests don't usually show a kid as very gifted if they're not at least mildly gifted but definitely miss some kids who are very gifted. CoGAT specifically says that they are not meant to test really gifted kids.
However, I personally know two kids who've taken the WISC IQ test more than once and had clearly average scores both times save for higher than average memory and processing speed indices and both hit the 95th percentile in one area on the CogAT scores needed for GT ids where I live.
That makes sense. I guess when I think really gifted, I'm thinking of kids who score in the very top (145 and up maybe) and I do think that not a lot of average (even prepped) kids score there. But yes, I guess I do agree that if the kids are really prepped, the CoGAT will be skewed to a certain extent. It's unfortunate because I think in some areas they are now requiring very, very high scores on group gifted tests and it will miss some smart, unprepped kids but let in more bright prepped kids.
