If your DS is ready for grade skipping or subject acceleration, when you present with all the evidence, the advocating part is easier.

Bear in mind that some schools may consider highly of IQ test but many more take above level tests such as SCAT, EXPLORE or SAT more seriously. Too bad, they do not have any test for 1st grader.

Talk with the teacher from last year. If he/she recommends acceleration/grade skipping, your path will be easier. If not, IQ score alone may not help you much.