After 16 years of banging the drum for state education and the comprehensive cause, Margaret Tulloch is stepping down as the spokesperson for the Campaign for State Education.

For years she has called for better state schools and championed the comprehensive school cause. Critics might say she sounds like a needle stuck in the groove of a song that has long had its day. But there are not many of them.

“Even if her views are not always welcomed, her huge personal charm and warmth mean that people know that they are to be respected,” says Martin Rogers, from the Education Network. “She’s committed, thorough and always willing to look at the evidence. She’s a really effective lobbyist.”

Former Labour Cabinet minister, Roy Hattersley, goes further. “She is absolutely constant. It is thanks to her that the comprehensive ideal continues to be an issue in the Labour party.”

She had a modest upbringing in east London, where she attended a grammar school. The experience left her convinced that the vision of working-class children getting on through such schools was not as rosy as was painted.

Education did not figure in her adult life until her two children, Alex, now 30, and Helen, now 28, started school in Merton, the south-west London borough where she still lives with her lawyer husband, David. Before that she was a mycologist, working at Kew on the cataloguing of micro fungi.

“And I’m very proud that my paper on this is still in print,” she said.

Although a Labour party member since her twenties, it was education that made her become a full-time activist. Before long she found herself meeting Bob Dunn, a Conservative junior education minister, to lobby for local mixed schooling, and was soon asked to join Case’s national executive in 1988.

Since then Mrs Tulloch has fronted campaigns for smaller classes, more parent power, and an end to outdoor school lavatories. More recently, she has spoken out against the “plain bonkers” regulations governing the ballots on grammar schools, brought in during New Labour’s first term, and the specialist schools programme.

The 59-year-old is deeply disappointed that her party has gone down the road of diversity and creeping selection.

“I really hope I live long enough to see the history of this period written up so that we can see who exactly had the influence, and how,” she said.

A practising Christian, she clearly tries to be charitable and in her statements is usually only “saddened” or “disappointed” by events. However, the courtesy is not always returned.

She was left shaking with anger this autumn when education minister Stephen Twigg rounded on her, accusing Case of never caring about the children in Thamesmead who did not get five good GCSEs.

Mrs Tulloch may have just become a grandmother but she intends to continue playing an active part in education politics as secretary of Comprehensive Future, a Labour party group campaigning for an end to selection. She is also involved with the Research and Information on State Education Trust, and is chair of the Advisory Centre for Education.

And as for Case: “It was there before I came and it will be there after I’ve gone.

“But things come around and around and when you find yourself thinking, ‘Oh, here we go again’ you think, ‘God, it’s time I went to the allotment’.”