I agree with what Grinity said. At three, it's hard to say how your child will react in kindergarten or 1st grade or what level they will be at 5/6 years old. It's also true that PG kids vary widely in how they respond to their environment and school settings/expectations.

My PG son is 5.5 years old (late birthday) but I had no idea that my son was PG until he was placed in a more academic setting. My son was in a integrated, special needs program until last Thanksgiving so our situation was a little complicated but yes, I have direct experience with him being placed in a teacher-driven versus more child-driven classroom settings in two gifted schools as a pre-k student.

Our son resisted the teacher-driven, traditional gifted setting or drill-and-kill approach. He whizzed through the prek/k/1st grade curriculum within 2-3 months and we were then told that the school wouldn't accommodate him or bump him up into the 2nd/3rd grade class. It was the speed/rate that my son was accelerating through the prek/k/1st curriculum that prompted the school and teacher to say our son was very likely PG.

Since March, our son has been in a creative/gifted school where there is 28 kids from pre-k to 8th grade in a one-room, type schoolhouse. This school is more child/older student-driven/ intrinsically motivated and suits my son better. Still my son only does pre-k work since he's a pre-k student even though he was doing 2nd/3rd grade math and work at the previous gifted school, which is somewhat frustrating.

I would suggest looking around to see what the public schools will do and what your other options may be in terms of private or homeschooling. Be open to exploring your options and re-evaluating the situation if things don't work out as you envision or plan. From my experience, you have to take things in very small increments and not plan ahead more than 6-12 months.

From 4-7 years old or more - any changes to the school setting can be changed and reversed. I found this article quite helpful - http://www.davidsongifted.org/db/Articles_id_10115.aspx

I wouldn't say that preschool was a complete disaster for us since our son was 2e and needed services but it definitely presented us with some challenges and frustrations. Our son has not always been willing to interact with age peers. He's had more success with interacting since moving to the creative/gifted school in March and able to work with older kids, but he still a control freak and tends to withdraw if he's not confident about the situation/expectations.