I think most of the parents in this forum went through the same thing. It is easier when the teacher recognize the giftedness of the student. It is hard to go in the battle (for differentiation) with IQ number alone (unless the number is >99.9 percentile or >145-150 depending on which IQ test).
The school will counter with how many other students who had the same IQ score as your DS. It would be beneficial to take above level testing such as SCAT (from John Hopkins CTY), or EXPLORE (from NUMATS or Duke TIP, etc..) although EXPLORE will be phased out after 2014 and SCAT starts in second grade.
My advice for you for the time being is do enrichment activities at home. My kids did Study island through school (the school got them their grade level but they could do above grade level because the account was not restricted), Khan Academy, etc....
And take SCAT next year. SCAT test is 2 grade above level and with the good score, you will have better chance for advocating for your DS. My personal experience was that everything started rolling only after my DD's SCAT test result. I am sure not every school operates the same way and I hope your school does better.
