If your child scored 99% on the MAP, it likely means she can already read pretty well and do basic math and may be entirely underchallenged in a regular 1st grade classroom. Also, accelerated and GT classroom doesn't necessarily mean academic intensive. For example, there is less homework at my son's GT school than there was when he was in the regular classroom. They are accelerated at least a year (so, e.g., they do 4th grade math instead of 3rd, so they're learning more appropriate material). I would investigate further into what the GT program is like if I were you. You may be pleasantly surprised.
Here's more info on NWEA MAP:
See p. 55 for Reading percentiles, RIT score; p. 67 for math.
NWEA MAP norms then plug the RIT numbers in here to see the types of things your DD is ready for:
RIT info 
