Sarah Elizabeth Jackson was born at Erdington, near Birmingham, Warwickshire, England, on 6 August 1858. She was the second of seven children born to Fanny Brittain Chapman and her husband, James Jackson, an earthenware dealer. The children were raised in the Moravian Brethren sect, attached to the Church of England. Sarah attended local day schools and a Moravian boarding school at Fulneck, where she remained until 1875. For the next year she worked as a clerk and bookkeeper with her father's firm until taking up a teaching post at the Bedford Moravian School.
A series of financial setbacks, ill health and a threat on his life forced James Jackson to sell his business and emigrate. With four of their children, including Sarah (aged 23), James and Fanny left London on the Wellington on 30 September 1881, arriving in Auckland on New Year's Day 1882. While the family moved to farm on the banks of the Waikato River, Sarah chose to remain in Auckland, teaching briefly at the Beresford Street School. In comparison with her earlier work she found the teaching 'mechanical and uninteresting'. However, her appointment as matron of the Auckland Industrial School in April 1882 marked the beginning of an interest in social work and the welfare of children that would dominate her life.
The Auckland Industrial School was run by the Department of Education. It received neglected, destitute, criminal and uncontrollable children who had been committed by the courts or at the request of their parents. As matron, and later manager, Sarah's duties were extensive. In addition to overseeing all aspects of the management of the institution, she was responsible for supervising children who had been licensed out from the school to employers. She remained in charge of the industrial school until her retirement in 1916 after 34 years of service with the Education Department. During this period child welfare was developing into a specialised professional field and the state was beginning to value children more and take greater responsibility for their care.
Jackson also acted as the district agent under the Infant Life Protection Act 1907, inspecting all foster homes and other institutions for children in the Auckland district and giving advice on the care and feeding of infants. She was regarded as a fine manager and was well loved by the children left in her charge. Her involvement in child welfare continued with her appointment in 1926 as one of the first women justices of the peace; she exercised jurisdiction for several years in the Children's Court in Auckland.
Sarah Jackson's personal life reflected her commitment to the welfare of children. She belonged to a range of philanthropic and religious groups connected with social issues, including the Girls' Friendly Society, the Order of the Good Shepherd, the Auckland Community Welfare Council and the Mothers' Union of the Anglican church. Her involvement with the church, always strong, increased after her retirement. In 1922 she became one of the first women appointed to an Anglican vestry in New Zealand, at St Alban's Church, Auckland.
Jackson shared the progressive social ideas of her time on the role of women. It was through her work for the Auckland branch of the New Zealand Society for the Protection of Women and Children, of which she was an executive member from 1916, that she became an important figure in the revival of the National Council of Women of New Zealand in Auckland. She was secretary–treasurer of the local branch in 1918, and held the position of secretary for most of the 1920s. She also served as president and vice president of the branch. Sarah was similarly active at the national level of the council. She was one of the three Auckland delegates to the first revived national conference of the NCW in 1918, and became the national treasurer in 1919, a post she held until 1929. In both the branch and national forums of the council Sarah campaigned for the welfare of children, advocating changes to child welfare legislation, the raising of the age of consent, and harsher penalties for those who sexually assaulted children and women. In 1933 Sarah's work was recognised when she was made a life member of the NCW, the third woman to be so honoured.
Caring for others also dominated Sarah's family life. Although she never married or had children of her own, she acted as a foster mother to several of her nieces and nephews from 1901, taking them into her home in times of death and sickness. Sarah Jackson died in Auckland on 9 November 1946, aged 88, and was buried in St Luke's churchyard, Mount Albert.