Point is, it's small enough to have its character changed rather easily ;-) (I do sort of agree, but you also have to know that acceleration really doesn't exist in the UK in state schools in recent years, and neither do gifted programmes, so when parents ask about either, they will be told to let go of the idea. From a US perspective, this looks off-putting; from a UK one, it is realistic.)
I've just quickly looked at mumsnet TAG forum (a few random threads) and I saw some posts in the direction of 'follow your child's lead' and 'some children level out and others don't' and other posts like 'let your child be a child'. Also I saw a pretty normal discussion of whole-grade skipping and subject acceleration. So that forum is not hopeless by any means. (I do find things more hopeless elsewhere.)
