The discussion of social mobility tends to focus on the institutions that are dominated by the middle classes, which is all of them, so it is a very middle class conversation. It includes people from working class backgrounds, but only those who chose to be socially mobile, not the far greater number who did not.
The discussion assumes that universities and high status professions control the level of social mobility by granting 'access' to working class people who, it is also assumed, all want to be socially mobile. In reality, the decision to relocate socially has nothing to do with universities or professions because it is taken at school, by children. It isn't fashionable to point this out, but the vast majority of poor children choose, in spite of the best efforts of their teachers, not to succeed in education.
When you examine this choice from the point of the view of the child it isn't hard to understand. Firstly, it is only available to those who believe themselves capable of competing academically with their middle class peers. Of this small, but not insignificant, minority of poor children our education system exacts a horrible price. It requires them to say, by their actions, to their friends and family: "I'm going to leave you behind in poverty and join a separate, higher, class of people. Goodbye losers!".
Social mobility is evil, a perniciously positive spin on the idea that some people are better than others. Yet its rejection by the vast majority of working class children is cause for great hope. Their choices disprove the Thatcherite notion, hard wired into our political debate, that people's primary motivation is to maximise their own economic gain. By choosing to fail at school the so-called 'bright' poor children are choosing to sacrifice material wealth and status to preserve family loyalty and friendship.
An increase in the trickle of people from degrading poverty to middle class respectability doesn't make us a good society; only equal pay and respect for all people regardless of occupation can do that. If you would call yourself progressive, virtuous or simply decent then make social harmony, not mobility, your goal.