I don't really see how they can 'allow' 25% of the boys to be from out of catchment because standardisation and the schools admission procedures don't allow for a specific percentage. Based on previous years it does seem likely that the OOC figure will be somewhere between 25 and 35% but it really can vary based on the number and ability of applicants who have sat the exam that year.
Everyone in catchment only has to achieve a standardised score of 334, so technically if 170 in catchment boys achieved that score then all of the places would be filled by in catchment boys. In reality that doesn't happen and a percentage of places do go to OOC boys every year.
I think the Exam Overview document from the meeting in June, states that approx. 25% of new entrants are from OOA each year, so I've miss quoted them by saying "allowing" rather than this is what eventually happens in most years.
Perhaps a number of those who pass from in area go to Manchester GS instead or somewhere similar meaning a larger number of OOA applicants than expected get places
Like you say the standardisation is a bit of the "dark arts" so it's less cut and dried
From the figures quoted does that mean only around 127-128 "in area" kids achieve the 343 score or do they allocate the "in area" places first from all those who met the pass mark and accept a place and then allocate the "spares" from those who passed "OOA" and live closest to the school
Not long until we find out