What other people have said is true, that generally the primary schools of Forest Hill are all fine. However, the secondary schools (and no doubt someone will take issue with this statement) are not.

Here are the 2011 league tables - which show the nearest secondaries, Forest Hill (boys) and Sydenham (girls) are barely bobbing around the 50% mark for A-C GCSEs. Better bets might be Prendergasts (girls) whch used to have an excellent reputation, although I gather it's gone down hill a bit recently, and Haberdashers (former grammar school), but also Kingsdale and the Charter school in Dulwich.

I don't know much about the entry criteria for secondaries. Kids do grow up incredibly quickly and unless you are planning to move again, I'd say that would be a good area for further research.