There's a certain amount of learning about taking tests that comes into play. DD6 went to a play based preschool which was wonderful, but her first school test results were much lower than her abilities. After a few months of learning about taking tests (in Kindergarten!! cry) the scores jumped up significantly.

I liked Grinity's phrasing about having a data point. Now you have a data point, but it's just a data point. It may be a good data point or a bad data point and has to be taken in context with everything else you know about your children.

Will the school accept outside testing? It may be worth spending the big bucks for an alternate assessment.