A few years ago, I was invited to Clare college, Cambridge to report on their admissions procedure. The college, which is an enthusiastic pioneer of ways to attract more state-school pupils to Cambridge, had introduced a new measure to help it distinguish between applicants: the exam results of candidates' schools. If the overall A-level results were poor, the student would have the edge over a similar student who came from a school where the results were good.
The measure played only a small part in a very thorough and complicated assessment but publication of the scheme's details caused a furore. Private school heads weighed in to denounce as unfair an indicator which might put their high-performing institutions at a disadvantage.
No one seemed to notice that the change, coupled with strenuous efforts by the college's admissions staff to ensure that every candidate, however difficult their background,had a fair hearing, led to only a tiny increase in the proportion of state-school pupils offered places.
Similar indignation greeted last week's announcement that the Universities and Colleges Admissions Service is considering a plan that will enable universities to retrieve socio-economic data about applicants at the touch of a button, including the GCSE and A-level success rate of their schools.
Independent schools argue that we should not be using generic data to determine individuals' future. In an ideal world, they may be right, but their protests rang a bit hollow the day after the biggest ever survey of students' backgrounds shows that the most affluent are six times more likely to get to university than the poorest. Other studies have shown that working-class students' chances of reaching higher education have improved little since the Second World War. Any progress is down to the former polytechnics, not to Oxbridge or other elite universities.
Schools do make a difference to pupils' chances of going to university.
Private-school heads cannot have it both ways. They tell us that their schools are worth the fees because they offer a better education than many of their state competitors. They speak proudly of their teaching, their facilities and their small classes. And they admit that they provide the last three because they have more money to spend than their comprehensive colleagues.
Yet when Ucas suggests that the advantages enjoyed by pupils at successful schools should be taken into account to make university admissions fairer, they are up in arms. Do teachers in inner-city Birmingham really have the same chance of helping bright pupils through Oxbridge hoops as those at Westminster and Sevenoaks? Do they always have the energy or resources to try?
The head of a comprehensive with above-average exam results told me that he sometimes wondered whether he should try to get more than a handful of his pupils into Oxbridge each year. He always rejected the idea because it would mean diverting teachers' efforts away from other parts of his school.
I hope that Ucas's plans to end the postcode lottery will help to tackle one of education's most persistent problems. But I fear that it will not: the gulf between successful and struggling schools, both private and state, is too great. Remember Clare college's experience. Independent schools heads may protest but I think it is unlikely that they are shaking in their shoes.