On a more serious note, part of me is tempted to believe the 'dumbing down' of British education is actually part of the elite agenda for the guaranteed maintenance of the status quo.
... In the best Orwellian sense. Consider Newspeak, and Orwell's explanation, in his book, of why it was brought about..
If you don't have a vocabulary, how do you engage with the concepts that words express, by their meanings? If you have an idea, how do you express it to someone else?
The answer is, you can't. The proletarian (again, borrowing from Orwell here) is docile, intellectually impotent, frustrated... and less of a threat.
Though, that said, I don't really go in for that vaguely militant leftist thinking anymore. I'm more inclined to ascribe it to a general wealth of incompetence, and some trends in modern popular culture. :)