Our son was offered a place in the Maths top set, he is extremely competitive and works very hard in school, maths is natural to him, English isn't. His level 5 in English was big surprise.
We know that from working hard and being top in the middle set, he will move into the top set and be middle, we have spoken in death with his maths teacher and with him, and will see how the first term goes. He doesn't have a lot of confidence in himself and we don't feel at this age he needs pushing any further, he is doing excellently where he is. The top set in maths is full of some incredibly bright children, of which, out of the boys, none are sporty, and we know that was a key in his reasoning.
His sport nerd mates (our sons passion is sport, he lives for it) are mainly in the lower maths set, and we are aware that he felt uncomfortable with finding maths fun, we suspect (we may wrong) after a term in the middle set he may well want to go into the top set come Christmas, as they wont be in class to influence any decisions. We just had to find a balance for him, for now we have.
I stumbled on this thread Out of total curiosity, searching for sat result posts.