"Although you may be right in saying there are no bad schools in SE23, that's relative"
I have to agree with Nutfield that all the primary schools in this area are good. I looked around quite a few, spoke to loads of parents, and I can honestly say I would be happy for my children to go to any of them. We are very fortunate.
In the end I chose the one closest to me because I do believe in being part of a school community, and also its ethos suited me, but I think its easy to get worried over the differences between them when actually they are all a good standard, and I'm not just saying that because I live here.

I know of parents in other areas of London where there are particular schools that you wouldn't touch with a bargepole, and I can honestly say I don't know any primaries like that near to me.

The differences between the schools are less to do with good and bad schools and more to do with the parent's idea of what a good school is - and that varies depending on what your personal priorities are (e.g. is it SATS? OFSTED? An active PTA? Demographic of other children? Focus on sports/arts/music? Size of school? Location? Playground? Uniform? Parents get quite het up about all these and can be strongly for or against each of them) And of course once a parent chooses and gets their children into a school, its fairly common they will praise their own school and criticise other schools!

So no, I don't think there are any bad schools here, at the moment anyway. Just that some schools suit some parents better than others.

Schools can change fairly rapidly depending on leadership so its quite hard to plan 5 years in advance; and the best way to influence a school is to get involved in the PTA/Governers, as others have said.

Lastly its worth noting that Lewisham's primary school results are overall good compared to the rest of London. We weren't aware of that before we moved here (pre children) we just made a lucky choice!