Exam takers from working class and long-term unemployed parental backgrounds will score lower.

Good point. And that is the problem with class-ism in the UK. The upper classes stick it to the middle and working classes each and every time. But what riles me more than those toffs like Boris Johnson and Cameron, are the faux champagne sipping guardian reading socialists, who have a high salary and a pension, and holiday in exotic places. Those are the really horrible hypocrites imho.