I wouldn't rule out a grade skip based upon him being younger for grade. One of my girls has a Sept. bd (so turned 6 shortly after starting 1st) and she did wind up skipping a grade later (5th). Prior to that, we found subject acceleration to work well for her. Subject acceleration entails sending the child to the next grade up (or more) for a single subject (or more than one subject) while still having him/her remain in the standard classroom for the other subjects.
Other than trying something like that, I'd look into when the school assesses for giftedness, what the criterion are to be so identified, and what types of services they provide for the kids who are GT ided.
My youngest (late Sept. bd) won't be skipping any grades both due to her age and size and b/c it isn't the best fit for her personality, etc. She is being subject accelerated in math and has a GT reading class daily that replaces the std classroom work. That seems to be a good fit for her and sufficiently challenging at this point. She's a bit erratic in any case, so we wouldn't want anything more right now.
Some GT programs don't replace the std classroom fare, though. Instead, they are things like weekly fun activities where the kids do experiments or play games. That usually isn't the best bet for fully engaging a gifted kid.
