I have just compared my DS grammar school's AS results for 2012 against its A2 results for 2013, ie among the same year group. To my surprise, there has been a significant number of subject drop outs (up to a third for languages and humanity subjects). The trend is that only those who managed to achieve an A grade for subject X at AS in 2012 were allowed to go on taking exams for A2 (plus 2 or 3 borderline Bs) in 2013.
My son has just started his Y12 and he told me that there has been a few cases of students being asked to repeat the entire Y12 to re-do the subjects if they didn't manage enough As in 'useful' A level subjects at A2.
I am rather concern that the superb league table position of high percentage of A* and A achieved could just be an illusion at the expense of their students. Culling doesn't stop at pre-selection before GCSE but continue discreetly in the sixth form. Is this process common in all top independent and grammar schools?
I don't know if it is common, but certainly it is very hard to compare A level results between schools as there is no indication of what the starting point was like at the beginning of the upper sixth, or at the beginning of the upper sixth.
There may be some wisdom though in asking a child who has only got a D at AS to either drop that subject or repeat the material. It's not a very good basis on which to commence the A2 work for that course is it? But requiring an A in everything at AS is a bit tough!