Newsnight had a remarkably short piece on this. They weren't exactly clear why they thought London did better but it seemed to be to do with teachers being married to other highly educated professionals. And there are more jobs for these people in London. Why that in itself matters I don't know. They did mention that Leeds is struggling to fill vacancies at the moment. Reading between the lines the suggestion would appear to be that the lack of graduate jobs in other parts of Britain makes it harder to attract teachers. Does this mean that those places can't be as choosy about the teachers they take on? Is it harder to get a teaching job in London? It wasn't entirely clear.