http://www.bbc.co.uk/news/education-12163929
The measure is of how many children achieve good passes in English, maths, a language, geography or history and two science qualifications.
I find it amusing that with my relatively poor GCSE results I would have achieved this but my wife, who did considerably better, would not; my B in Geography trumping her A* in RE.
This sums it up for me: http://www.bbc.co.uk/news/education-12171281

