"*We've receieved a lot of kickback from her homeroom teacher and the district math curriculum leader. They don't appear to believe us when we say she learns super quick, she's not being challenged, she's mentally bored, and that she needs to learn how to exercise her brain regularly. "

The data points they are going by are actual performance in school. Your data point is...what?

I don't see how factual evidence from a widely accepted testing process can be anything but beneficial, assuming you're trying to get to the correct answer and accurate facts.

The cost time and effort were certainly worth it to me - a few hours, a few hundred dollars to get my child into the right educational path for the next decade of her life? Seemed like a pretty small investment to me.