The MAP is split into the three different groups, and there is some overlap, but it is not like you can just keep going and getting the higher level complete test if you don't miss anything when you're in a lower level. E.g., if you are taking the 2-5 test, and you answer everything correctly in a category, you will get some questions from the next level (6+), but you will not get all of the questions. Thus, if NWEA says a 235 qualifies you for algebra, if you look closely it probably has an asterisk that says "a 235 on the 6+ test", where you get all the questions.
If your kiddo is getting all top scores, I would ask that the next time he be tested on the next level (2-5 or 6+ as applicable). Then you can get some more meaningful data beyond the fact that your kid is way advanced for his grade level.
Also, you can look at this website to see what sorts of things a kid who gets a particular score should know and what they're ready to learn next.
http://www.powayusd.com/projects/edtechcentral/lladder/Default.asp
