Tanner was born in 1876 in
Bath, the eldest of seven children of Samuel Thomas Tanner (1849-1929), of 6, Leigh Road,
Clifton, Bristol, a coal merchant and
magistrate who worked with the Bath
Board of Guardians, and Jeanetta ("Nettie") Jane, assistant in a "high-class draper's", and daughter of George Fry, of Lynton, North Devon, sometime grocer, farmer and "post-horse proprietor". Her younger sister, Beatrice Tanner, a nurse, was awarded the
Royal Red Cross medal in 1919. Her parents, despite their wishes, could not afford to fund advanced education She became a student teacher aged thirteen and spent her time teaching in private schools until she was employed by the ''Ladies' College, Halifax'' where she was trained. Tanner arranged her own education and submitted herself to the University of London where as an external candidate she obtained a first class history degree in 1904. The following year she was working at
Sherborne School for Girls.
Nuneaton High School for Girls was founded in 1910 with the strong support of Warwickshire's Director of Education
Bolton King. Tanner was the founding head. She enjoyed the support of Bolton King throughout her career and she joined Nuneaton's Education committee. She led the school in Nuneaton for about a decade and then she moved to
Bedford High School where she again joined the education committee in addition to bringing reform to the school. Tanner was poached from Bedford to lead
Roedean School in 1924 by
Penelope Lawrence, one of Roedean's founders. She joined the education committee in Brighton. She had already been one of the four women on the consultative committee of the Board of Education and as head of Roedean she was asked to serve on that committee for another six years. Tanner was Chair of the Association of Headmistresses and later their President from 1947 to 1939. ==Damehood==