US politics has become so mean-spirited and polarised that not even the esoteric world of education policy scholarship appears to be safe.

So when Diane Ravitch, a high-profile research professor at New York University, was dismissed from her unpaid position as a fellow of the Brookings Institution thinktank after seven years, speculation quickly arose that her criticism of Republican presidential candidate Mitt Romney was to blame.

Professor Ravitch described Mr Romney’s education proposals as “a rehash of Republican education ideas” in a long contribution to The New York Review of Books blog. Just four hours after the blog was posted, she received an email from the Washington thinktank’s director of education policy, Grover “Russ” Whitehurst (an adviser to the Romney campaign), informing her that she had lost the position.

In a statement, Brookings says the decision to cut ties with Professor Ravitch and two other senior fellows was made in April, well before the blog appeared.

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The reason, it adds, was that “in each case, the fellows had little contact with the programme and were not involved in programmatic activities. Their scholarly views had no bearing in the decision.”

“I never speculate about motives,” Professor Ravitch - who was appointed to public office as assistant secretary of education by Republican president George H.W. Bush - told ����Vlog.

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But she added: “Whatever the motivation, and I don’t know what it was, the claim that I was inactive is absurd.”

A prolific writer, Professor Ravitch is the author most recently of The Death and Life of the Great American School System: How Testing and Choice Are Undermining Education (2010). When it was published, she said, she asked Dr Whitehurst if Brookings would host a discussion of the book.

She said Dr Whitehurst had told her that she would have to pay to rent the auditorium and cover significant additional expenses. The book event was in the end hosted by Washington’s conservative American Enterprise Institute at no charge.

Two years after its publication, the book remains a best-seller on Amazon’s list of works about social and public policy. It is strongly critical of George W. Bush, for whom Dr Whitehurst was education research director.

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“There was nothing more I could do [at Brookings] without being asked to be involved,” Professor Ravitch said. “I never was. This in itself is odd, since I am arguably one of the most active participants in national and international debates about education.”

She said the reason given in the Brookings statement seemed odd grounds on which to “terminate an unpaid senior fellow…It’s not as if I was a drain on the institution.”

Professor Ravitch wrote that among Mr Romney’s rehashed proposals were plans to support school vouchers subsidising parents whose children go to private or religious schools, to hold teachers accountable for students’ test scores, and to lower entrance standards for new teachers.

But she has also been consistently scathing of Arne Duncan, Barack Obama’s education secretary.

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“Brookings should be sponsoring debates and panels about the very issues that I raise,” Professor Ravitch said. “It is now clear those debates and panels will never take place. That is sad, far sadder than my termination.”