It is quite possible that your district uses local norms. The system routinely calculates district-wide (by grade-level) and school-wide means and standard deviations, so all the data for generating local norms is clearly accessible to a district that chooses to use them. Depending on the composition of your district, his percentile could be markedly different on local and national norms. His actual RIT scores should be the same.
MAP also allows for customizing the start date of school (and thus how many weeks of instruction a student has received at the time of assessment). It is also conceivable that a boilerplate scoring using the default start date may compare a student to the wrong group, with the result that the percentile obtained from the correct comparison group is different. For instance, if a district starts school in the beginning of August, students assessed there have had nearly four more weeks of instruction than have those in a district opening after Labor Day. Especially at certain grade levels, and for certain skills, comparing them to the same norms may give the early-starting cohort a little bump in the percentiles.
If the percentile difference is slight (and one point would generally be considered slight), then it is likely due to something in the category of the situations I've described above. Of course, it is disappointing to be on the wrong side of a one point difference. It may or may not be worth additional advocacy efforts, depending on your district and student circumstances, but if you do choose to pursue further advocacy, the tiny difference in percentiles is probably not going to be a productive focus for your efforts.
