Do you have an option for changing schools to another district? They may be more cooperative if they think your child may move (not necessarily, but sometimes). We only received offers of accommodation after contacting the district superintendent. I wouldn't have thought to do that (it seems like something that might annoy principals and teachers and make things difficult). However, the testing coordinator told me to call the superintendent after she saw my daughter's scores and the superintendent told the curriculum specialist to work something out. Part of the reason may have been that we had decided to move DD to another school, but we were offered some substantial accommodations at that point.
As far as not starting until third grade, I think many schools say the same thing. It doesn't mean they can't do anything earlier. They often start standard pull out programs then, but those often don't offer that much anyway. My DS is in kindergarten in a district that doesn't have GT until third grade, but they have brought in the GT coordinator to consult for him. I think that is reasonable when you have clear evidence that something more is needed. One thing I was told, which seemed helpful in explaining the scores, was to say that a child with an IQ of 150 was as different from average (100) as a child with an IQ of 50. Would they be comfortable having a child with an IQ of 50 in a regular classroom without accommodations for learning differences?