The public school gifted coordinators (at the district levels) were very nice and accomodating for us. We had variable results with private schools. However, if it is a school for gifted students, they'll be used to "gifted" parents.
I'd begin by just approaching them to learn more about the school (including a tour), to find out about admittance criteria (incl. school testing vs. private testing), and waitlists, etc. Then after you've been nice and you are sure you prefer it to homeschooling, you can start pushing for early entrance, etc.
Most schools in our area require applications in December and have made their decisions by March so you are right on time for a Fall 2010 start.
