The concept of political correctness seems first to have emerged in Sixties America as a well-intentioned attempt by leftish liberals to discourage the use of words that gave offence on grounds of gender, sexuality, race or disability. It took root most firmly in the educational sphere. There it led to pressure for curriculums that, for example, viewed history more from the perspective of ethnic minorities. It overlapped heavily with feminism and, to a lesser extent, with the movement for positive discrimination in favour of minority groups.
To the delight of the political right, it soon laid itself open to derision by attempts to propagate a series of ludicrous euphemisms, such as calling the disabled 'differently abled' or the short 'vertically challenged' - though it was never easy to know which had been dreamt up by humourless ideologues and which by satirical detractors. No less welcome to the right were the PC-mongers' attempts to correct what they saw as an educational bias in favour of Dead White European Males (Dwems), presumably including Shakespeare; and their tendency to espouse the homosexual cause.
What had started as a movement to eliminate the offensive use of words such as cripple and spastic, and to sharpen awareness of gender bias in such words as mankind, soon lent itself to portrayal as a new brand of censorship and thought- policing. The backlash has been effective: the abjectness of the headteacher's apology yesterday was a measure of her misreading of the present mood.
The biggest failing of the PC movement has been its complete lack of any sense of humour and proportion. Where feminism has survived its own extremists, the PC movement has died of derision even before establishing itself in this country. The Hackney headteacher is just another of those who helped to kill an essentially sound idea.