Hi callaghan, welcome! A couple thoughts. The MAP test is actually pretty great, in my opinion. It is an open-ended test, meaning that they don't end the test when you hit a certain point at your grade level. You can keep going. See Appendix B here to find out where your son's very high scores fall in other grade levels.
http://www.nwea.org/sites/www.nwea.org/files/resources/NWEA_2011_RIT_Scale_Norms.pdf For example, 229 in math for spring is in the 97% for 3rd graders. The big question is how the school handles this information. Are they teaching your son at his level? There are some things he can learn on his own, but he must be exposed to some concepts to do well in other areas (including a lot of math). If the school groups kids of like abilities, or differentiates, maybe it doesn't matter what his IQ is. (But since you said you have been fighting with the school for years, my guess is they are not doing the greatest job.)
Are there other schools in your area that you would consider? I agree with the others who said to make sure that your school, or whatever school you consider, will accept outside testing. Personally, I was happy to get information about the level of giftedness of my kiddo, so I learned to be prepared for lots of advocacy, flexibility, and accommodations. The testing was helpful to us - the school recognized that our son would need more than usual, and even though the formal GT program didn't start until 3rd, they started doing differentiation in kindy for our kiddo.
