ALEKS.com has a free trial, and they have the skills they test broken down by state standards. You could have her take the ALEKS placement test for 3rd grade math (and 4th grade math, and 5th grade math, if she keeps testing out...) and print out the score results to give them a specific idea of what she has and hasn't already mastered, and the school can then directly compare her skills to their curriculum. And it eliminates any vague objections about "gaps" because you can see exactly where those holes and gaps are, and fill them...
Just a thought.