Two schools are tied neck and neck at the top of the tree when it comes to GCSE performance among grammar schools in the latest school league tables.
Queen Elizabeth's School in Barnet and Colchester County High School for Girls both achieved 100 per cent rates of students getting five A*-C/4-9 grades in 2017-18.
They were by no means the only school to achieve this feat - in fact 46 schools matched it - but they come out ahead of the pack when ranked on a secondary measure.
Pupils at both schools made considerable progress when compared with students of similar prior ability at other schools. Both had a Progress 8 score of 1.22.
Our interactive league table allows you to peruse these rankings and search among the 163 selective grammar schools in the Department for Education's data.
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While scores of grammar schools managed to get all of their students achieving over five top GCSES, only 14 managed to gain a Progress 8 measure greater than one.
The Progress 8 measure aims to capture the progress a pupil makes from the end of primary school to the end of key stage 4.
It is calculated for each pupil by comparing their Attainment 8 score (pupils' attainment across eight qualifications) with the average Attainment 8 scores of all pupils nationally who had a similar starting point.
A score of zero means that pupils on average do as well at key stage 4 as other pupils across England who got similar results at the end of key stage 2 - so a positive score means that their progress outpaced that of similar students who used to be at their level.
Changes in GCSE regime meant that a new numerical system was used to mark most subjects, something that is still being phased-in.
In an attempt to toughen up GCSEs, the new system uses grades one to nine, rather than from A* to G - with anything above a seven being level to anything above an A in the old system.
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Note: Secondary schools have been ranked by the percentage of pupils achieving five or more A*-C/ 9-4 or equivalents including 9-4 in both English and mathematics GCSEs. If schools are tied on this metric, the Progress eight measure is used as a secondary ranking.