Welcome jsmom! Jane was right. You have to have a book or the online version of what he's being taught! Let them know that you would like a book along with the scope and sequence of what he's being taught. Every district I've ever seen follows a specific published scope and sequence or grade level expectations. You can usually get the basic ones at the state level but have to get what your specific school is doing week by week from them.
FYI-the schools don't always follow the state requirements. They follow the books. What this may mean for your accelerated son is that the 3rd grade requirements by the state may say "student's will understand time to the minute" and your son's book may be teaching elapsed time which is a 4th grade skill. So not passing a lesson may or mean he's not passing the 3rd grade skills which is already an acceleration or it may be even higher levels. This is what I found when my son accelerated. It took me a year to figure it out because no on tells you about it and honestly the teachers don't even realize this discrepancy. Once I figured it out I made the teachers aware of it.
You may also want to print out a few article on the asynchronous nature of a gifted kid. He's not going to be as mature as a 3rd grader. He's going to be a regular 6 year old in many ways. This is normal.
And on the truly gifted studen't not needing help with math. Nip that in the bud! Obviously she has serious misconceptions on gifted education. Again. I'd bring article from experts stating the exact opposite and quote them. Then leave her with copies. Gifted kids are more advanced than others which doesn't mean they don't need any instruction. I might make the point of quoting her back and asking her if this means she didn't teach him the skills that he failed. I'm sure the principal will set her straight on that point.
Hang in there!
