It's hard to be fair on such things.
If I take my dd1 who's currently applying.
She has been to state non-selective schools all the way up. They get reasonable grades so are considered "good" state schools.
We live in a "good" postcode.
She has not had any, nor would have expected to get any, contextual offers.
However she has friends who have had contextual offers.
The difference can be as great as A A A down to BBB. (that's the most extreme she's come across)
Some of these friends have been to exactly the same schools as her, and live in a "poor" postcode, at least one of them has only recently moved.
She's also got a friend who went to private schools all the way up, lives in the same postcode as us, but has transferred to a "poor" state school for the 6th form, but parents are putting the money instead into intensive tutoring. She's got some excellent contextual offers.
How do you, without knowing the individual cases, make these cases fair?
How do you compare a good private school, a good state school, a poor private school, a poor state school.
You can have a poor state school that does amazingly by their top ones-my df went to a secondary modern, having failed his 11+. They gave him individual tuition and he was the first (and as far as he's aware only) pupil to do A-levels there. He would still have done better at the grammar school probably.
You can also have a good private school that pushes the top/bottom and ignores the middle as they'll achieve good enough, but not outstanding to boast about results.
You can also have a child who's parents decided to spend their inheritance on private schooling, along with scrimping and saving to afford it, despite having little education themselves. They need extra support too.
And how do you compare a private school education, where they have 15-20 in a class, no disruptive pupils and selected so no children who really struggle, with a "good" state school with 30+ children in the class, some of whom will need help with basic literacy, some have SEN behavioural issues etc?
I support contextual offers. I support Oxbridge trying to identify people who would benefit and be academic enough, but whose exam results will be effected by their circumstances. I want to see the situation where people can be brought out of their background (as my df was) by hard work and support.
However I'm not sure it wouldn't just be something else the middle classes learn to manipulate to their advantage.
How do we identify those pupils who genuinely will benefit? Don't know!