Beyond that, I can really only share from our own experiences. My son was an early K start, who had an additional acceleration in 3rd/4th. He's had subject acceleration thrown on top of that starting back in 2nd grade (and gradually increasing over the years). We have the added bonus of our son being tall, so even with his age tatooed on his forehead, most people tend to forget that he IS actually younger.
I tend to agree with Kaibab that acceleration for a very gifted child does very little to actually challenge the child. For my son, it was about making school work at all. Lock step for him would have been insane. I was looking at some typical 8th grade algebra stuff last night....a course my kid shouldn't be taking for another 2 years, and there is no way he would have survived with his sanity intact, even a few years back. As it is, he's in a much higher math course and still coasting. But the volume/level/etc isn't outright ridiculous. He's learning new material, working a little bit, etc.
We're in an almost similar amount of acceleration situation with our oldest dd to what Dottie described. She wasn't an early admit to K b/c she made the cut-off but only barely. She did a combo of various options including subject acceleration and homeschooling before skipping a little later down the road: 4th to 6th. For her, the math in 8th grade accelerated algebra is totally appropriate for her right now. Literacy has been the primary area where I could say the same as what Dottie said about math: she has been capable of much more than she's been doing for pretty much her entire school career, but she's not miserable and it isn't a total waste of time this year. Many of the years have been, though. If I had followed her preschool teacher's recommendation to wait a year to start her in K due to her bd (which is common where I live w/ bds near dd's), I can't even imagine how poor the fit would be, though. Our dd will graduate high school at 16 as well, which is the most we're going for as well.
The amount of acceleration your grandchild is looking at sounds more significant. The only person I know who accelerated that much was my grandmother and that was, obviously, a long time ago. She was born in the early 1920s, started K as 4.5 and skipped both 3rd and 5th grade. She was tiny - 4'10" as an adult. From what I understand, it worked well for her but school settings are so different now a days that I don't know that her experiences would be transferable to modern schools.
Did they come to a decision and how is it going if so?
