Hi SusieIA, welcome!
It's a little difficult to answer your questions re: what to ask the school and whether a grade skip is warranted based on just the info you have given. Is your son having any issues with school? From the very little bit you've mentioned, it sounds like the school is actually pretty responsive if they moved him up a grade in math based on MAP scores. Do you feel he is still underchallenged? What sort of company does he have in his classes (i.e., are there other kids scoring similarly, or is he a group of one)?
The Math MAP math scores are quite high, and it sounds like the school is trying to challenge him by moving him up a grade. How is that working out? Depending on the curriculum, the teaching, the other kids at the same level, he may need even more in math.
The reading is high, 94th percentile for 3rd graders, but based only on MAP scores I wouldn't recommend a grade skip. The Iowa Acceleration Scale can help you get more information about whether a grade skip is warranted. The IAS considers many factors, including above-level testing, IQ scores, social factors, etc.
See Appendix B here for a comparison of where your son's scores fall compared against other grades:
http://www.nwea.org/sites/www.nwea.org/files/resources/NWEA_2011_RIT_Scale_Norms.pdf
