I'd go with the full skip because one teacher also means one set of kids. The 3 classroom scenario would make me worried that he would never "fit in."

If you did the skip could he get pulled out to get help with his speech and/or writing with support staff? Like the kids who get "remedial" support. Then he could work one on one with someone who could work around his schedule more and help him catch up to his intellectual peers.

Warning: sleep deprived