...if its results are simply a reflection of the fact that the school is full of children who are bright, middle-class, and well supported at home?
Really sick of people locally talking about particular schools, which they haven't visited and don't know anything about, in these terms.
A 'good' school IMO is one where many children make progress above what might be expected when they arrive at the school. Such a school might actually be quite low in the borough league tables because of having a disadvantaged intake.
It's all about what schools do with the children they have.