Kenny Frederick, a headteacher and member of the NAHT executive, has accused the Education Secretary Michael Gove of wanting to "bring us back to 1950s".
Speaking on the BBC's Radio 5 Live, she said that Mr Gove has not listened to teachers and that his plan was destined to "fall flat on its face".
Mr Gove is expected to receive an angry reception when he speaks at the NAHT conference in Birmingham this afternoon.
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The position, posted on the British Monarchy website, pays £16,000 a year for 20 hours a week.
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I think it is fair to say that was the best speech I have seen David Cameron give in the decade I have been reporting on him.