Hello Irisheyes! Thank you for your response. It seems like he can read some of the words he's spelling, or at least that he's intentionally trying to spell a particular word, but mostly I think he's just playing. For example, after he spells a particular word several times, he'll start doing it upside-down and backwards, like he's seeking a greater challenge. I am a little concerned, but more confused. When I mentioned his interest in spelling to their early intervention teacher last week, he said "Oh, lots of our autistic kids like letters." I guess I'm not sure whether to put this in the "autistic trait" or "gifted trait" column in my head, if that makes sense.
Sorry if I'm rambling -- I'm running on about 3 hours sleep this morning and I think I need some more coffee!