I've known kids that
a) Haven't score high enough on Cogat, and did the next time
b) That haven't scored high enough on COgat, but a psych administered WISC and the child was DEFINITELY gifted
c) Hit high 90's on one section and 4% on another section.

A child may or may not do well with Cogat. I wish schools offered another option like portfolio.
Tammy