Bullers Wood (girls) is very good, as is Darrick Wood (coed). You have to live quite close to them to get into the schools.
Beaverwood, which is now known as Chislehurst School for Girls, (or Chislehurst Girls School?) is fast improving. It's very near the border with Bexley, so is popular with Bexley people who didn't get into the grammars, as some of the secondary moderns are not very good.
Ravensbourne is "up and coming", as well.
Langley Girls in Beckenham is very good, but again, you have to live quite close by.
If you are CofE, you might get a place at Bishops Justice (coed).
Coopers doesn't have a good reputation, and I know a teacher there who believes there is a big problem with discipline, and the SMT not backing teachers up.
The Priory and Charles Darwin are not very popular.
If your DD is quite bright, there is Newstead. However, a lot of people don't like the new head, and there is some uncertainty about what is going on there, as she is currently away for "personal reasons".