visit the schools and see for yourself. Here's my impression of
Graveney (wandsworth), Kingsdale (southwark), Chestnut Grove (wandsworth), and Dunraven (lambeth), Charter North (southwark) are the choice of the aspiring middle-class. They are always oversubscribed. The only one that I liked when visiting was Graveney but none of them did much to impress prospective families and frankly after visiting a lot of other schools I think they're falling behind other schools. Many of these schools use all their co-curriculars as selling points but fail to tell you how hard it is for most children to access activities because they are gatekept for the more able.
Elmgreen (lambeth) really impressed with it's warmth and pastoral care as well as it's academic offerings. It seems to becoming really popular and the distance catchment is shortening. It was my son's first choice. I know lots of teens there - one complaint I've heard of
The Elms Academy (lambeth) was also a pleasant surprise on visit. But are more strict which makes it marmitey - however their results are quite good.
I also visited Haberdashers Borough (southwark), St Joseph's (croydon), and Westminster City (westminster). I quite rated Westminster City. It was our first preference but it's boys only.
I did not visit Trinity or City Heights. But have since heard positive things about them. Trinity is a small school and City Heights has a new head who seems to be turning things around. There was another thread which had more info. I'll see if I can find it.
It's really important to visit the schools with your child. What we read about schools is very different from what they are like. And a lot of the reputations are based on what the schools were like rather than what they're actually like now.