Obviously going to continue, as the privileged want to defend their privilege, no matter what it seems, so here is the first, and we will continue with SGordon's last red herring.
That's the whole point: making both sorts of data available makes it possible for people to see for themselves the extent to which socio-economic factors explain school performance. If you're going to claim that socio-economic factors are the reason a school performs badly. then you should be expected to back up that claim. And if you can't, then I don't see why covering up the performance of bad schools is in any way helpful.