lol, english p might know different but i wouldn't think schools would suggest it unless there was a very obvious difference in ability between the child and their peer group - otherwise they would all be doing it... quite a lot of children would be more than capable acaemically i imagine, (all of those top 3's at the end of KS1 for starters)
i think a school would have to take the cohort into consideration - to move one child essentially means that for some reason the school feels they would be unable to cater for that child's needs within the existing group... or that they are extremely enlightened and just feel that the child would be better off (which i would say just about never happens but would be willing to be proved wrong).
there would have to be an extenuating circumstance where it was considered necessary for that particular child - so either working at a much higher level than the peer group across the curriculum, (in this instance requiring constant access to KS2 materials rather than moving 'up' for specific subjects etc), or having parents who were keener than most to recognise and extend their child's attainment...
tbh it's the right time if it's going to happen - a child who has surpassed the KS1 curriculum and achieved top 3's at the end of yr1 isn't going to gain a lot by cruising through yr 2 where everyone else is working towards SATs assessments (formal or otherwise)
i'm just not particularly comfortable that it is done on such an individualised basis. many very able children wouldn't be offered this option, so for her to be offered it either means she is streets ahead, or there are other variables (parents etc).
i'm very interested though, why socially in this country it is considered more acceptable for a parent to approach the school and ask for little johnny to be kept back a year as he isn't coping, than it is for a parent to approach the school and say they want little molly to be moved up a year because she is bored rigid and mastered quadratic equations in her lunchbreak in yr r...
obviously the answer as to why neither happens frequently is rather more to do with systematic convenience than all children being identikit learners lol, but it is interesting what little peculiarites get built in along the way...
funny old world.