Self-knowledge closes the gap
But when this voluntary-aided selective boys' school started looking inwards, rather than comparing itself with other schools, the picture looked less rosy. There were significant variations between departments, with pupils taking French, for example, gaining many more A and A* grades at GCSE than those studying German.
In an attempt to bridge these gaps, the school set up partnerships between departments. So French and German worked together, as did history and geography, PE and design technology, and English and science.
Staff in each grouping started observing each others' classes, as well as holding joint meetings to discuss areas of common interest such as supervising coursework. Headteacher Peter Kent stresses that the idea was to share the good practice that exists in every curriculum area, and not to impose one department's way of doing things on another.
"We found that departments that were already achieving highly were very receptive to new ideas and those that perhaps needed to look outside and see what others were doing were also open to new ideas because it was all done in a non-threatening way," he says.
The impact of this collaboration has been startling. In 2003, when the partnerships were set up, 61 per cent of students taking French gained A and A* grades, compared with just 15 per cent doing German - a gap of 46 percentage points.
Two years later, the gap had shrunk to just 12 per cent, although both subjects saw an increase in the number of students gaining top grades.
Other pairings also produced impressive results.
At A-level - where the school doesn't select students on the basis of ability - a similar pattern emerged when staff teaching media and business studies began working together. "There was a big gap when we started, with media having a much higher value added measure than business studies," says Mr Kent. "Over the period of the project, that gap closed markedly through a similar set of processes."