I wonder if it would help to find a preschool that is play-based so that the emphasis is on social skills, and there would be no boring cognitive/academic stuff for him to be forced into. I remember my kids at that age and thinking that I'd rather have them just play all day at preschool than be forced to "learn" the alphabet or numbers yet again.
We had an IQ test done on DS when he was 3--the neurodevelopmental pediatrician gave us a referral to one of the psychs with the same Children's hospital. I don't think it was all that accurate since DS wasn't that cooperative, but it can be done. They weren't trying to figure out if he was gifted though. It was more an evaluation of delays (in his case speech and motor).
