One question in my mind as a UKer is, what school options are you considering for secondary school? Regardless of the skip issue, it'll have to be a pretty special school to cope with your mathy DS I would think - that's a speed issue, isn't it, so that even if a skip got him to a level where he started the year at the same level as his peers, he'd still go much faster than them and need extra by the end of the year. And many secondary schools are not as good as primary schools at being flexible. So it might possibly be worth approaching this backwards, by thinking about secondary school first. E.g., if an option were to send him to an independent school taking in at 13, then possibly you might send him there straight from primary (if that's where he is now?) school at 11, getting a two year skip there? But a plan to do that might suggest a particular kind of path now.
