I have a friend whose 3 children all went through Warren Road - the last has just started secondary. The head used to take out the chosen few for what I think she called masterclasses - i.e. 11+ Prep. I think the head may have changed now though. And my friend feels that the standard of education has declined as her children went through. Certainly the first 2 passed Kent 11+, the first well enough to get into Dartford Grammar (boys) and the 3rd, who seems equally bright, failed.
Warren Rd. stopped doing masterclasses 2 years back after the new headteacher arrived. Even those masterclass were quite elementary. I wouldn't say that the standard of education has declined. It was never geared for 11+, that's how I see it.
The boys who got into Olave's, Judd etc were all heavily tutored. I think the total into Olave's has gone down from 9 (2012), 5 (2013) and again 5 (2014). Some of them are my students, that's why I know the stats.