Dude and NCPMom, I'm pretty sure she meant 3yo preschool year, and 4yo preschool year, not 3 to 4 years of preschool.
Kristie, if you can find a play-based preschool that does not teach academics, that may be a much better option than an expensive private preschool that teaches more advanced academics. Unless that more expensive preschool specifically caters to gifted children, you may find that the academics there are still too slow for your DS. A play-based preschool lets your child focus on social skills and learning through play, and accomodates children with a very wide range of abilities. Many of us on this site have had success with play-based preschools for our children, and both of mine are/were really happy at our play-based preschool.