Mia,
The advantage of a single gradeskip is that he gets to hang with kids who are more likely to get his jokes. The material may at least reach the level of "edutainment" if not challenge. A disadvantage can be more paperwork and no more challenge. An advantage can be that the child is moved to a mental catagory of "we need to be flexible with this one, he's different," so permission may be granted to pile subject accelerations, independent study or online classes as substitutions. It seems hopeless, but every little bit might really help. I remember when a early admission to the Math Club, 30 minutes once every 2 weeks made a major difference in my son's life. Is that sad or what?
Welcome and Best Wishes,
Trinity
