you have little choice but to play the game
Stanley, the point the OP is making - I think - is that this is not a 'game' that can be played.
The school is using a 'possibly somewhat objective' ranking / screening process - based on predicted grades - to make 6th form offers.
However, the student's current school has a very significant impact on this measurement, because there is no uniform way of coming up with predicted grades:
- Some schools set targets, not make predictions - so they use FFT + SATs results + chose one of a number of levels of 'ambition / challenge' to automatically generate target grades.
- Some schools give 'stretch' predicted grades.
- Others give 'minimum' predicted grades.
- Still others give grades based on mock exams which are full GCSE papers.
- Others give predicted grades based on internal exams which are only on work covered so far.
Even once this variation is negotiated, the motives of the current school will affect teh predicted grades to be used for this process.
- Some schools will want to be able to boast 'we send X of our students to the most selective 6th form each year', so will tend to give high predictions to be used for application.
- Others will want to retain their own students so will give low predictions to be used for application.
The 6th form, meanwhile, doesn't have to work very hard. They have an oversupply of applicants, almost all of whom will be able to reach the 'real' requirement of 8 7s, so they don't have to worry about these nuances. They COULD work really hard to analyse the prediction vs actual results patterns for each school and apply 'fudge factors' to each set of predicted grades. Or they could just take the predictions at face value, knowing that it's OK, they'll get lots of bright students whichever way they do this.
Meanwhile a very able student who goes to a school that sets 'minimum predicted grades' and deliberately understates predictions slightly to avoid losing able pupils to the more selective school, misses out on an offer while a less able student who goes to a school that sets 'aspirational' predicted grades, and likes to boast how many students go to the selective school each year, gets one.
Certainly in the school I know of, the 6th form intake is 'lumpy', with many students from some schools and many fewer from others, despite this not really matching the actual GCSE results profile from these different schools.