As aeh suggested, my son is ahead of grade (entering 1st this year) in all his academic work, but classified as "developmentally delayed" in social-emotional skills and has an IEP. If you have access to an advocate, I would recommend talking to one familiar with your district. It sounds like they are not really classifying students appropriately if they are denying consideration of an IEP because his grades are good. You might want to poke around wrightslaw.com, too.

Good luck!