As far as I know, "ability" testing pretty much entails what you've already got: an IQ test. If the school has some issue with the specific IQ test she took, the WISC should be a reasonable alternative. I can't think of any other test you could have her take that would show what she is capable of learning and not just what she has already learned.
You might want to check with the school, though, to see what they need to see in order to offer her more at school. You don't want to put out money for more IQ testing if they won't do anything more if the results are similarly high to her last scores.
