Does your school administer the NWEA MAP test for math? If so, this is a great test to show above level math ability. Also, with a score on this test you can look here:
http://www.powayusd.com/projects/edtechcentral/lladder/Default.aspto see what math skills correspond to which scores and what skills are ready to be worked on.
Do you have his end-of-year math test from last year? If he aced it, I'm not sure the principal has a leg to stand on to keep him from continuing with the acceleration.
Another thing to consider when looking at his scores on any math test are not just how he compares nationally (percentile) but also how he compares to others in his same grade and in the grade into which he is accelerated or want him to be accelerated at his particular school. For instance, I know my DS's MAP score is in the 90th percentile nationally, but compared to other in his same math class, he is among the very highest scorers. However, if your DS goes to a school with a lot of kids of a similar ability level, then acceleration may not be as important. If he's at the top of his accelerated grademates in math, then it's hard to say his acceleration shouldn't continue.
Good luck with your meeting!
