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The middle school principal doesn't seem to give much weightage to the norms in NWEA's large test population.

Do you know what out of level tests he does consider? Unfortunately it's tough to find ways to magnify the tail end of the curve. Out of level is one way and another is the norm group.

This reminded me of a past discussion about Bassetlover's 7th grade daughter's scores on the SAT and MAP. Her percentiles compared to 11th graders were lower on the SAT (82%-90%) than the MAP (97-99%) because the SAT Norm group is college bound vs. the MAP which is all students. The SAT magnified things more because of the different Norm group.

http://giftedissues.davidsongifted.org/BB/ubbthreads.php/topics/43733/1.html

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For now, what is missing from school, we supplement at home; I hope with this arrangement, his MAP RIT scores will still show growth. We'll see.

Sounds like it's been working well so far and you're on the ball in case things change. I hope I'll be able to say the same when DD7 is in 5th grade.