My son is not behind in any subject either. We also could not get an IEP because of his grades and assessment scores. He did/does qualify for a 504 due to his autism spectrum and anxiety disorder.

At first the school told me he wouldn't qualify. I immediately contacted an educational advocate. Luckily I didn't need it and the school went ahead and approved his 504 without my needing to push.

This is the website I used to find a local advocate:
http://www.parentcenternetwork.org/allregions.html