Hi Michael,
It does maybe sound a bit like a mismatch of person, your son, and environment, preschool. My son just started preschool as well (he just turned 4) and it is not going very well. Just recently the teacher took me aside to tell me that he doesn't play at preschool and said that it seems like he doesn't know how to play. Since it is a play-based preschool this basically means that he doesn't do anything for most of the time. The teacher tried to assure me by saying that "some children are just behind in their development". We are, btw, not talking about playing with other kids here. He is behind with that. But playing in general has never been a problem. He started pretend play way before you'd expect and he can spend hours doing this at home. He loves Lego, does puzzles and logic games and visual-spatial games such as Super Mind and Rushhour. Most of the games he plays are age 8 and up. Like your son he reads and does some math. At preschool they now go on a letter hunt every day in order to learn the letters. My son knew those when he was 1.5 years, just like your son.
The other day I asked my son what he likes most about preschool. He said "When I learn new things" "Great" "Not so great - they never really teach us things. Do you know when they are going to start teaching us chemistry? And I am really exciting about learning more math". So I told him that this school is for playing. You should have seen the look on his face. Utter shock and despair. His eyes welled up and he said "But Mama, why did you sign me up at the wrong school? You know how much I love learning!" Since then he cries every night that he doesn't want to go to preschool any more.
I have thought of asking the teacher if we could donate some more appropriate toys. But I think she'll say no. Because these toys could not get used by most of the other kids and might be frustrating for them.
I am considering pulling him out and instead enrolling him in some courses and group things as he does need the social experience.
So, I do think this might be a normal reaction of not knowing what to do with himself. Is there a way you could get him to spend time with other gifted kids his age? I think often these kids do "tick" differently and it might feel nice to find like-minded kids. If my son could find another boy to talk about the periodic table of elements and do experiments with I would love that!
Hang in there!
Stefanie