Kelly,
From my experience with schools, most of them don't really understand or acknowledge IQ scores. They certainly don't understand when a child is several standard deviations beyond the 100 IQ mean. They seem to mostly look at achievement tests. I'm not familiar with the NWEA, so I don't know if it gives beyond grade level testing, which is what the second psychologist is recommending. There are different kinds of achievement test. Some stay within grade level (but will report higher grade level scores, such as "If a 5th grader took a 2nd grade test, he would get this score), and some truly go beyond grade level. It is possible that your school doesn't understand this difference either.
The most effective way of communicating my son's needs with his school was to have his teacher give him the end of year assessments or tests for each subject when he was in second grade, around the beginning of October. If you can show that your child has nothing new to learn in that particular grade, then you have a case for the school to take action. Each child deserves the right to be appropriately challenged in school.
Please note that they will try to insist that your child must get a 100% on every test to show mastery. This is incorrect. Most school require about an 80% on end of year tests to show mastery of the material. If you child passes this level, you can then ask for the teacher to administer the end of year tests for the next grade up. That should give them an idea about the appropriate placing of your child in their school with their curriculum. Plus, it is free!
But the only reason to start pushing along this path is if you really want the school to take action. Usually parents will request subject acceleration or a full grade acceleration if they show that their child is not fully challenged at school. The best thing about this is that it does not require any form of gifted funding at your school. If your school is willing, they can give your child an appropriate education by just allowing her to be in the appropriate grade, even if it is just for a single subject like math or reading. It requires no extra work or money on their part. But that is a pretty big IF.
This is just one more perspective on a very difficult problem that has many different solutions. I hope this helps?
Ebeth