The NNAT is a brief, non-verbal test. I know my son's score on that matched his scores on the Woodcock Johnson, the KTEA and the PRI section of the WISC-IV.

I don't think any of the brief tests can really claim to be super accurate. They are like little snapshots. If you want an accurate picture, you'll need a test like the Woodcock Johnson or the WISC.

~amy