I don't know if you're in a position to do so, but I'd question the policy of not giving students the 6+ test. Because we use MAP tests to help determine what a student needs to learn next, when I see a MAP score that has few/no "next steps", I switch kids to the 6+ test. It's possible that the student's percentile might drop, but I pay more attention to the RIT score than the percentile in these cases. I've also given the 2-5 to K/1 students.
I would also second what Cranberry said - you really want to be focusing on trend data rather than individual points. When students are flirting with the ceiling of the test, the odds that their score will go down on the next administration are pretty good. When this happens with my students I show parents additional data to show that their child made growth during the year. No one test should ever be the sole arbiter of whether or not growth was made.
I love the MAP test because it helps to pinpoint what a student needs. MAP scores near the ceiling (and this is more of an issue in reading than in math) are not always great indicators of growth or the lack of growth.
