My DS will turn 4 in December. He is very bright, although we have The curriculum doesn't go past introducing letters and numbers. I have a kid who wants and is starting to learn to read and write, knows letters and numbers, does addition and subtraction in his head. Plus he wants to learn about things in depth - he doesn't want to just learn his colors, he wants to understand why red is red, and blue is blue...
To be honest if he attends a regular preschool and you move him to the 4 year old class it's very likely that he will not be taught how to read or add or do other things he wants to learn. I am afraid that your and his expectations wouldn't be met anyway. He may be in better social situation and make more friends but the academics would be still off. Of course there are still schools like Montessori but even those may not work well (like in the case of DS4)
From my personal experience preschool works best as a place to play and interact with other children. If your child understands that he can get as much learning as he desires at home and the goes to PreK mostly to play and have fun, then he may be ok with the situation.
