It's surprising what effort teachers used to put in to try to prevent working class people from getting on. We would be constantly told that doors were closed to us, that we would be unhappy or uncomfortable if we tried, that there was no point in trying. H was told he should go and work the mines like his dad. I wasn't allowed to do A level English on the basis that 'You would have to read books'. This is despite getting a double A in English at O level. Middle class kids with much lower grades than me were allowed into the class. But more than this overt discrimination, it was the sour looks and discouraging words.
I think it was to try to overcome these barriers that the school league tables and so on were instituted, and the attempt to extend Higher Education to a very high proportion of school leavers. It's a crude and perhaps even destructive lever, but it was an attempt to address a hidden exclusion which must have affected millions of young people like me. The ones who were less aggressive and bolshy than me probably took the teachers' advice and went to work in a factory.