Search the forum and you'll find tons of posts about this. I don't want to repeat everything I've written in the past for lack of time right now, but the Iowa Acceleration Scale is a good place to start.

Don't wait until the end of the school year if you are planning this. They need time to make a decision and have all of the facotrs in place or they may simply deny your request due to lack of planning time.

Also look at the acceleration institute website.

Good luck!