How/where do I get DS tested for IQ/ability, and which test/s should be used?

DS was tested by the school when he was four using I don't know which tests (can't find the paperwork right now--they were not the standard tests), then tested again last year with the OLSAT and the ITBS for entry into the Gifted/Talented program. None of these tests measures IQ as far as I know. He is currently seven years old. Is it important to know IQ (for education reasons) or no? Should I be trying to get outside testing for DS so we can get a more specific measure of his abilities? The objective is to secure more appropriate day-to-day educational opportunities for him in school (like acceleration in certain subjects). He is generally not allowed to participate in gifted classes/camps because he has Asperger Syndrome. Our not-so-great public school and private tutors are our only options.