Regardless, DYS accepts both WJ academic achievement and WJ cognitive. It's more likely a public school will administer the WJ-III academic achievement test rather than the cognitive (IQ) one. Both tests will give you data and information on your child.
WJ cognitive is an IQ test and will give you more information on processing speed; the WJ academic achievement will give you information on the reading, writing, and math levels.
If you're public school system doesn't have the WJ academic achievement test, try to see if they have one of the other ones listed on the DYS criteria page -
http://www.davidsongifted.org/young...holars___Qualification_Criteria_384.aspx