In general, I would say it is much better to skip 2nd grade than to skip 1st grade and to not skip the entry point to a GT program. It is less stressful on the kid and it makes sure that he doesn't miss crucial transitions at optimum times. Having said all that, I think it makes sense to skip 1st grade in your DS' case for a host of reasons, including he is old for grade and average-to-above in size and he appears to be academically oriented.