I believe the WJ III percentile reporting is a CRT reporting. Which means it has a cut-score of what is considered "average". Only I don't know what that cut off is and even if they would release that to us mere mortals. I think you are safe to assume that 99% is fantastic!
You may try EPGY. My DS6 scored 98 percentile and started it 2 months ago. DS^ started out at the beginning on level K since that was how my particular sign up agreement worked. DS6 completed level K in one day. DS6 does 20 minutes about 3 times a week and has progressed to level 2. Loves it and I suspect we'll get through level 4 by the end of the year. Not bad for a 6 year old.
