I could be wrong (in which case someone will correct me!), but the research I've seen recently points to good early/worse late (i.e., high school) results for kids who are held back. I'll see if I can find the link.
If you suspect giftedness, I'm not sure that you would see better test scores, reading outcomes, etc. -- he may already be ahead of age peers by K.
FWIW, we did not even consider holding back ODS (PG, though we didn't "know" it then) despite a very late summer birthday. It made absolutely no sense to us to consider it given his intellectual development. Nor will we hold back his May birthday sibling, who isn't yet at that level of academic progress (that ODS was at by this age) but whose preschool teachers say is more than ready.
You'll have a better idea where your child is at by this time next year. Is there a reason to worry now?
