Consideration against what? I'd expect gcse location to be considered for WP, but that's only one tiny thing
Considered against both the performance of the school and the pupil’s cohort.
It’s quite clear in the admissions information:
Cambridge: We will look at your GCSE results as an indicator of your academic performance. But this will be within the context of the performance of the school/college where you achieved your GCSEs.
Oxford: The performance of your school or college at GCSE. Your attainment at GCSE compared to GCSE attainment at your school or college.
Nothing to do with quotas and everything to do with trying to game the system by moving to state for A levels in an effort to get more favourable consideration. This was spotted and addressed a long time ago.
Are you really admitting that you just hate kids who have ever been to private school so much that you want it to always count against them forever?
Give over. You’re the one thinking that private school students can get some kind of leg up by moving to state for A levels, and now you’re finding out that’s not the case so you’re resorting to declaring that I must hate privately educated students.
I think that all students should be considered on their merits, but that doesn’t mean that it shouldn’t be recognised that it’s not a level playing field.