We haven't grade-accelerated our ds, but we have run into many similar issues over the years. One thing I regret having done but just couldn't see past it at the time was thinking that we had him in the "best" school choice. We selected his first school for all the right reasons, and it seemed in theory and in its advertising and teacher-speak to be a school where differentiation would happen, where students were encouraged to work at their own pace and levels and where the teachers really cared about the kids. I trul loved, and still do, the ideas bend the school's philosophy, but it didn't work formy ds and hoping to make it work as we stuck it out for severa years was simply wasted time while ds was bored and unhappy. So my small piece of advice is, ask for what you think yours needs, fight for it, and if you don't get it -look elsewhere. JMO, but I am guessing this particular teacher isn't going to be convinced no matter what documentation you show her. Hopefully the principal will be more open-minded.
Re documentation, I've found achievement testing that ties to state curriculum to be the easiest and most convincing piece of documentation in advocating for acceleration (although our ds isn't grade-skipped he is multi-grade level subject-accelerated). Having the IQ tests as backup doc that ability matches achievement has also been helpful, and perhaps most important thing -understanding what the tests and subtests represent, understanding how to interpret them has also been very important when advocating.
Sending you lots of good wishes!
polarbear
