I'm thinking that you might get further if you try two things:
1) First check as to whether there is a district GT coordinator with whom you can consult and find out what type of test results they are willing to consider when placing a child.
2) Get some quantitative proof and not just teacher and parent assessments. Can you have him take an achievement test that will allow him to show above grade level achievement such as MAPs, WJ, or WIAT? The MAPs might be a good way to go b/c it is really comparing apples to apples: a 7 y/o who gets a 240 is showing the same functional level as an 11 y/o who gets a 240. Other achievement tests will give you something like a grade equivalent that shows more how a typical 11 y/o would have done on a test designed for a 7 y/o, for instance.
I'd also look into IQ testing or some sort of group ability test other than what they've given if you can afford to do so. I, personally, greatly prefer IQ tests to group tests, but the group tests are a lot less expensive.
