Our DS was given the Woodcock Johnson III test by the school at the age of 5, when it came time to skip him over kindergarten. It really doesn't start until age 6, but the computer allowed them to norm the test for his actual age and for "Kindergarten 9th month" as if he had finished Kindergarten already, which was the earliest they could do. It skewed the grade equivalency scores a bit, but he was already so off the charts it didn't really matter. Yours would probably do the same. It was a really good test for showing skill levels across the board.
