Sarah Kirby was born at Ipswich in Suffolk, the daughter of the painter John Joshua Kirby, who served as president of the Society of Artists, and his wife Sarah. Young Sarah attended boarding school in Ipswich. In 1755, the family moved to London, where her father became a tutor to the Prince of Wales. Sarah made the acquaintance of painters such as William Hogarth and Thomas Gainsborough, as well as that of Samuel Johnson. In 1762, Sarah married John Trimmer of Old Brentford, and the couple had 12 children. Sarah Trimmer drew on her experience educating her own children when she become active in the Sunday School movement, which taught adults as well as children to read. She was consulted by Queen Charlotte, who founded a Sunday School at Windsor. Books written specifically for children were only just becoming popular, and Mrs. Trimmer helped to define the genre through the reviews published in her periodical The Guardian of Education, founded in 1802. Mrs. Trimmer also wrote numerous children’s picture books and educational manuals.