You'll have to dig a little, but there is a ton of information on the official site.
www.legacysupport.nwea.org as well as assorted sources from various school districts.
Anyhow, from my previous readings, the maximum rit score appears to be 320 on MAP math and 300 on MAP reading. However, it is rare to see scores near these hard ceilings so I have seen references to 300 and 280/290 as the "ceilings" for math and reading respectively. Furthermore, for Spring of 11th grade, you only need 286 to hit 99th percentile on MAP math and 266 to hit 99th percentile on MAP reading. Note though that you need 290 to hit 99th percentile for end-of-course Geometry students. I think it may be that you are dealing with a slightly higher ability population there. Furthermore, there is a suggestion of possible soft ceiling effects at much lower levels. I believe I have seen 245 for reading, which by my extrapolation would be about 265 for math.
HTH
Disclaimer: Please don't accept these numbers at face value as I am obviously too lazy to bother pulling the sources that I had previously investigated and am relying on memory and patterns in RIT scores (which are equal interval).
