I don't know whether this will be of help to any of you or not, but my older children have friends who have been/are finishing at Graveney, Chestnut Grove, Dunraven and St. Cecilia's, as well as Lady Margarets, Emmanuel and the Tiffins.
At each and every school all but one of their friends have done well at GCSE level and are all on track to do the same at A Level this year. At Chestnut my friend's twins were there until 2 years ago - one did amazingly and the other failed miserably.
When we were all going through the whole secondary transfer nearly 7 years ago, Chestnut Grove was the one that we all absolutely said a firm NO WAY to. However, some did go (no places elsewhere) and although the first couple of years there were something of a nightmare, once they hit Year 9 it changed dramatically for the better.
One of my DD2's great friends from primary (we were around Northcote Road) who went on to Sacred Heart in Hammersmith and did extremely well at GCSE there this summer, has just started at Chestnut Grove having been absolutely bowled over by what they have to offer her for 6th form.
My older three are now Years 13, 12 and 10 (they board out of London), but DS wants to go to sixth form in London and I will absolutely be considering Chestnut Grove and Graveney as my first choices, lots of his chums from primary are at one or t'other, and we will be moving back to slap in the middle of the two in a fortnight.
I'm dreading this all coming again with DD3, but first I have to get through the whole finding a bloody primary school crap again with her for her start in 2 years. To say I'm crapping myself over that is something of an understatement; I fear it is ten times worse than when I was doing it for DD1 in 1998.