My ds6 had the WJ cog administered by the school psych a few months ago to go along with his other evals for an IEP. Looking back only that short time, I am thinking more and more that his scores on the WJ cog will probably turn out to be a huge underestimate of his IQ, whether due to his performance or due to the way the test is organized, etc. He scored significantly higher on the WJ achievement test, which really doesn't make sense. And since then I know for certain that his achievement scores would be even higher still if he re-took it now - it just so happens that he has hit some sort of developmental growth spurt and has made huge gains (in reading in particular) since that testing. He is quite the late bloomer, and I see changes almost daily these days.
I guess my two points would be (1) I really don't care for the WJ cog - my sense is that might not be particularly reliable; plus I find the WISC much easier to understand (and one day when we test ds privately we may even do the SB5); and (2) some kids can change a lot in the early years.
