Coming in late to this thread, but I wanted to comment in a general way.
Overall in the US, educational options for HG+ kids are woeful. The law forces public schools to focus on lower achievers. Worse: too many schools and teachers don't understand cognitive giftedness. Our curriculum is based on textbooks that are often subpar. Private schools can be better, but then again maybe not, and not everyone can afford them. Etc.
Forums like this one can help, but personally, I've noticed a trend here that can encourage people to skid. By this I mean 1) a focus on what may not be the most important questions, and 2) that an idea grabs hold and the negative side of it isn't taken as seriously as it should be.
With respect to point 1, I wonder about all the test result threads that have been popping up here in the last year or so, and if they're creating an unhealthy atmosphere. Tests are important, but they're only a small part of an overall picture, and besides, it seems to me that the person who did the testing would be in the best position to interpret a child's disparate scores or answer questions about his/her performance.
A good example of point 2 is acceleration. When I first joined this forum, people talked about it (or homeschooling or whatever) as a least-worst option. I don't read so much about that idea anymore. Instead, I read a lot about the positive aspects of accelerating, with negative ones (e.g. the OP in this thread) being downplayed: no really, my kid fits better with kids who are 3-5 years older. That fact may be true when the topic of conversation is chess club or Jane Eyre, but it's simply FALSE when a 12-year-old is bundled with 15-year-olds who spend a lot of time talking about dating, athletics, staying out late on Saturday night, and etc. etc. It's important to consider how the 15-year-olds feel about the little kid in their midst, or about the 12-year-old's level of comfort with those kids.
I still struggle with how best to challenge my kids, and they've struggled with the consequences of being much younger than grade-peers. I've had two co-worker friends who were radically accelerated and the OP's statements mirror theirs. Yet I get a sense on this forum that there's a groupthink at work, and that it's dismissive of this very real problem. I wonder if we have some emotional overinvestment in acceleration (subject or whole-grade), test results, and a feeling that a course of action is essential because someone else took it.
I'm just trying to write as someone who's been around the block a few times and who's seen what happens when a skipped student gets to middle school, high school, or college. It's tough. And IMO, the literature from gifted groups over-encourages acceleration and glosses over the negative sides of it.
It's easy to get caught up in the ideas of giftedness and challenge, but the reality is that the motivation has to come from inside, and 6th grade math in 3rd grade won't put it there (and maybe won't even force a HG+ kid to have to work to understand the ideas anyway). Many gifties hit a hard wall when they get to college and have to work hard to keep up and/or don't get an idea the first time it's presented. So college is one stage of life when the student has to dig down deep and either develop internal motivation or not. Sure, s/he may be motivated to work hard at activity A, but life is full of tasks that are a means to an end, and many are hard to master. For a giftie, struggling to learn to do them well can be a hard lesson, and those of us who are HG+ ourselves are all trying to help our kids avoid some of the problems we had. Acceleration seems like a natural option. But at the same time, we need to listen to the people who were accelerated and not trade one difficult situation for another.
Understand, I'm not saying Don't accelerate! Don't test! I'm just saying that I think that the focus here has become skewed, to the detriment of the whole community.
Finally, my best results have always happened when I turn off the emotions and the ego. That might help a lot here.
