Annette,
My son is one of those that is radically accelerated. At 8, he should be looking forward to 3rd grade. Instead he will be taking 2 7th, an 8th, and 2 9th grade classes this year. It works for him because of who he is and where he is at.
He goes to a very small charter school that is located on the campus of our university. The entire student body are self identified geeks (don't ever call him a nerd). They don't pick on him because they were all picked on at some point. Last year when he started, he was an anamoly for a couple of weeks. Now the other students treat him just like everyone else. They seem to have forgotten he's 5 years younger and 2 feet shorter. Sounds odd but it's true.
His school is set up to offer dual enrollment whenever it becomes needed and if he ends up in a college classroom at 10 it will be because the faculty at his school deems it appropriate. The difference is that because of his age, he will be escorted to and from his college classes and still have the full support of his current school. It is the perfect situation for DS and I count my lucky stars everyday. Who would have thought that a program like this could possibly exist in a state ranked 49th overall for education?
The key to all of this and to any of these kids is flexibility. You have to be willing to make short term plans and have long term hopes because everything can change over a summer. I would think long and hard before I would allow this kind of acceleration in the general population of a public school. I know that it wouldn't work for my son. You have to look at the individual and make your choices based on him and him alone. We can all share our experiences but just like any other population, they are all different. You know him better than anyone, you have to gather as much information as possible, cross your fingers and make a choice.