Comprehensives, Isobel Shepherdson insisted, do as much for the brightest children as selective schools. She believed all children made incalculable gains from being educated together and energetically promoted her view throughout her headship of Kidbrooke School in South London, the first purpose-built comprehensive, and in lectures and writing.

Isobel was born in Leeds in 1927, the only child of Mary and Frank Shepherdson, a policeman. She went to Thoresby High School, then, after a period of wartime evacuation, to Roundhay High, also in Leeds. After reading English literature at the University of Leeds, Isobel returned to Thoresby where, at the age of just 22, she was appointed head of English.

More promotions followed, with her first headship coming in 1963 at the high school in Brigg, North Lincolnshire, where her sports car caused great interest at the school gate on her first day.

She stayed there for seven years, also serving on the LEA education committee. “The education department was terrified of her, the parents were terrified of her, the students respected her and we all loved her,” one colleague said.

In 1970, Isobel took on a different challenge when she was appointed deputy head of Kidbrooke School, succeeding Dame Mary Green as head three years later.

Isobel trusted her staff, which stood her in good stead through a decade of immense change, not least during the transition from all girls to a mixed intake.

She maintained the aura of headship, and kept such traditions as starting governors’ meetings with sherry and leading assembly in her gown. But she was also very good at connecting with staff, governors and parents and brought a warmth to her role. Isobel would never have described herself as a radical, but any stand she made was principled, and she encouraged innovations such as the study of feminist literature, multicultural studies - which brought a National Front demonstration to the school - and a pioneering student trip to Israel.

It was one of her idiosyncrasies, beloved by those close to her, that she combined a keen eye for what she saw as the important stuff of life with a loathing for high-tech: she wrote in pen and ink, on paper, until the end. This included handwritten messages on the order of service for the funeral she had planned.

Isobel took early retirement in 1983 and moved to Kilham, in the East Riding of Yorkshire. She continued to lead a full life, supporting the arts and becoming active in the Women’s Institute. She brought to this work the same passion she brought to education. It was perhaps in this same spirit that she declined the offer of an OBE.

She continued to campaign, notably for equal opportunities. She was an avid letter-writer, and lectured and wrote until ill health intervened. She died in York on 6 February, after a fall.

Margaret Peacock is head of Chestnut Grove School in Balham, South London, and a former head of English at Kidbrooke School, where she worked with Isobel.