Born in 1853 in Plymouth, Amy Key was the daughter of Joseph Henry Key and his first wife, Elizabeth, both of Cornish extraction. She was educated at Newton Abbot - where the family had moved in 1857 - and then at a small boarding school in Whitechurch. Key was employed as a governess from 1869, publishing her first work - a short story in the magazine Good Words
- that same year. In 1873 she joined the staff of the Plymouth High School, after taking a first in the Cambridge "Women's Examination." She read Mathematics at Newnham College from 1875-76, while on leave from her post, and returned to teaching at Plymouth from 1876-80, at which point she became the first Headmistress of Truro High School.
During the course of her time at Truro, Key earned an external MA from London University, meeting her future husband, London University lecturer and tutor Henry Clarke, in the process. The two were married in 1889, and had three sons and one daughter. That daughter, Amy Key Clarke
, would go on to become an author and educator herself, teaching at Cheltenham Ladies' College, and publishing a history of Truro High School that included a memoir of her mother. After her marriage, Clarke continued to lecture occasionally, at Westfield College, but devoted herself primarily to her family and her writing. She died of cancer, in 1908.
Clarke's work is mostly in the field of historical fiction for adults, often set in Cornwall, although she also authored a number of novels for younger readers, many of which demonstrate her keen interest in the subject of academic education for girls.