My cousin Kath Hart, who has died aged 78, was an authority on mathematics education. After working as a secondary teacher in Britain and abroad, she joined the team developing the Nuffield Primary Mathematics programme in 1960. The resulting course, which focused on understanding rather than rote learning, was used in about half of all primary schools in England.
In the 1970s Kath worked as a teacher-training lecturer and a Unesco adviser before joining a research team at Chelsea College, London, where she led the mathematics part of the influential Concepts in Secondary Mathematics and Science. This, and similar projects she directed, produced substantial new insights into how mathematical ideas were understood by secondary pupils. It brought her international recognition and a visiting professorship at King's College London. The resulting book, Children's Understanding of Mathematics: 11-16, became a bestseller with significant influence on educational practice and research. An early member and later president (1990-92) of the International Group for the Psychology of Mathematics Education, she promoted rigorous standards of research in mathematics education and touched the lives of children and teachers around the world.
She was born to working-class parents in Whitechapel, east London. Her primary schooling was fragmented by the second world war, but, as a beneficiary of the 1944 Education Act, she went to Hull University.
Kath's ability to talk in clear English, her empathy and her hard work ensured that she was highly regarded worldwide in the field of education. She became professor of mathematics education at Nottingham University in the 1990s and colleagues valued her support, effectiveness at fundraising and commitment in supervising overseas students. Her deeply held Catholic faith and socialist principles informed everything she did and many students were helped by her, practically as well as academically.
Even after retirement, Kath worked and travelled; two months before her death, and in the late stages of cancer, she gave seminars in Bangkok. She was a governor of her local primary school, looked after her mother in the last years of her life and introduced her nephews (and many others) to world travel.
Kath was a loyal friend, over decades and continents; she loved opera, theatre, a glass of wine or a G&T and talking. She cared about you, especially if you were a child, and she widened your world.
She is survived by her brothers, Tony and Mike, her four nephews and their children.