I don't really know the answer to your question. But I can tell you that our school was enormously more open to the idea of giving my son an IEP after they tested him than to giving my daughter one after we had her tested. Does he already have an IEP/504 plan?
I think it is also easier to find an outside professional to administer a different IQ/achievement test after he is tested by the school, if needed, than it is to convince the school to use an "unfamiliar" instrument because he has already been tested with the one they typically use.
