Some of the many issues I encountered was that the school (perhaps reasonably) felt that I couldn't possibly skip out on physical exersize classes, or sex education, or any of the various things I would be missing. So they scheduled me into these classes with my own age-group, and then tried to fit the rest of my schedule in around that...
This resulted in me being placed in whatever classes I could fit in. Many times, in those classes that are set and arranged in order of ability, I was only able to be scheduled into some of the lowest sets. Some of my classes, such as chemistry, I could only attend less than half of the lessons because of catastrophic scheduling issues. In others, I was ignored by the teachers, and struggled to fit in with any peer groups.
In terms of social skills, I wasn't exactly bullied physically, just had almost nobody at all interested in talking to me aside from the person I was accelerated with - people were well-meaning and nice enough, but it's not exactly 'cool' to hang around with somebody two years younger than you around that critical time of vying for status, so I never really got into any longer conversations or made friends.
By the time I left, I pretty much considered myself somebody who was socially isolated with extremely poor social skills, and 'weird' in some kind of fundemental way. A lot like some of the other children that had learning difficulties were. It wasn't until I got to university and had a fresh start that I realised I was actually relatively socially capable in all kinds of situations, and it was mostly the school setting that had contributed to that view of myself.
I'm not entirely against this kind of thing, but done wrong, it can definately have a massively harmful effect on a child's education. While I have recovered somewhat in my professional career, by my academic results, this 'experiment' was an appaling failure. My peer at the time hasn't been so lucky as far as I can tell, and they did not manage to get into any universities at all. If this kind of thing is to be done, it needs to be done with care and constant attention on behalf of the school's staff.