Earlier quoted context omitted.
Intelligence and knowledge are two different things. An uneducated person may be highly intelligent but have little knowledge.
ok - in that case: when I switched to a white collar job suddenly all the world's knowledge was unlocked in my brain, and I knew the meaning of all these terms that had heretofore been opaque to me.
Some exceptions I've seen are people like my mother who grew up higher-class but 'defected'. Another exception is occasional disabled members of the working class.
It has nothing to do with the intelligence or ability of the working class as a population and everything to do with the fact that people in that class who have certain abilities and types of intelligence are offered a way out that others aren't. (e.g. A mechanical genius is less likely to get this treatment than a kid reading several grades ahead ).