Grrrr!
How frustrating for you.
Here's a whole section about NWEA accuracy and comparisons to other measures.
http://www.nwea.org/assessments/researchbased.aspI did my own comparison with DD6's NWEA MAP scores and out of level Stanford Achievement Test. Her +1GL Fall MAP and +1GL Stanford scores gave identical percentiles for math and reading.
You may want to look in terms of his growth too. It sounds like he had huge growth from Fall to Winter. Do you have his past NWEA MAP scores to show how he's moving up the above grade level percentiles too? You could make a table showing his GL percentiles, +1 GL percentiles, and +2GL percentiles over time.
I looked up his above GL percentiles here on page 143:
http://pickens.it.schoolfusion.us/m...ssionid=14d1e9266e4482d198ebc39c6e6bc9c3 That Math RIT score give GL 99%, +1GL (3rd) is 96%, +2GL is 79%, and +3 GL is 54%.
Another point you could make is that Johns Hopkins CTY uses 95% NWEA MAP scores as an eligibility guideline for their Talent Search. I don't think they would accept random 3rd and 4th grade math tests.
http://cty.jhu.edu/ts/tests.htmlOf course you have to be careful how you present this if she's intent on proving he's not gifted. You could say, "Have you considered his above grade level percentiles? Here's what I saw when I looked into it more."
Do you have the Student Report that shows the graph of your son's growth compared to the district and national norms? The picture of the "gap" may help too.
Good luck! We had a similar issue earlier this year, except it went a bit further because the teacher had been given bad norms. The scores were used against DD6 being gifted when they thought she scored low. When we showed the norms were bad and she scored high, the story switched to "NWEA MAP is only used to guide instruction and not for identifying gifted." Now it seems to be worked out with the teacher at least.
