Patty,
Sorry, I�m still scratching my head.
Are you in the Southern Hemisphere by chance? Otherwise the score should be reported something like this:
S08 RIT 162 = (4-22-08 April 22, 2008 or end of 1st)
You can see that here:
http://www.powayusd.com/projects/edtechcentral/MAPS/PDFs/00-04-05 Student
I�d ask the teacher if you could get a copy of your son�s NWEA MAP Student Progress Report before the meeting so you can digest the information before discussing the best course of action. That report will also have the percentiles which will help put his high growth in perspective. If you can�t get a copy from the teacher before the meeting, I can help you create one if I were clearer about the dates/season/grade.