They standardise the scores so that a certain number pass - for Pate's 160 children are deemed to 'qualify'.
It isn't a percentage that pass nor is it a fixed number of questions from the test that need to be correct - the top 160 (for Pate's) qualify - irrespective of their test score.
A couple of marks can be added according to age for the youngest in the year but no gender difference is taken into account at all.
The mark required to be in the top 160 at Pate's this year will have been higher.
The other schools do exactly the same they just pass / 'qualify' more students because they knwo their brightest candidates opt for Pate's.