Something similar happened to my DD this past fall on the NWEA and I posted here about it as well. It turned out her lower score was the portion of the test that she took when she came home from school with a 101 degree fever. I talked to her teacher about it and confirmed the actual date of the test and it was indeed the day that she came home from school sick.
Was your DD sick during the time that the math portion was administered?
At conferences her teacher said she was glad I had made the correlation and that is why it is so important not to categorize a student based on a single test score.
