Emily Sophia Brittan was born in Sherborne, Dorsetshire, England, on 18 December 1842, the eldest of six children of Louisa Chandler and her husband, William Guise Brittan, a newspaper editor. In 1850 the family travelled to Canterbury, New Zealand, as cabin passengers on the Sir George Seymour. They arrived on 17 December in Lyttelton, where they stayed briefly before moving to Christchurch. William Brittan became commissioner of Crown lands for Canterbury in 1853.
Although Emily had attended a small school in England, her education was neglected in New Zealand. However, intelligent and self-motivated from an early age, she began her own studies. Helped reluctantly by her brothers, who attended Christ's College, she learned Latin and Euclidean geometry. She persuaded her father to give her lessons in Greek, persevering until she could read it with ease. Studies were fitted in around household duties and looking after and teaching younger siblings. Emily considered homemaking an important part of a woman's role and just as important as education. By the time she was 12 she held a small Sunday school at Avonside church.
In the early 1860s the family moved to Halswell, where Emily taught Sunday school. Louisa Brittan was unwell and the burden of household responsibilities fell on Emily. The Brittans moved back into Christchurch in 1870, where Emily helped at Addington School. Here she worked with Thomas Scholfield Foster.
Emily Brittan obtained a second-class teaching certificate and in 1873 was appointed mistress at St Luke's School. Ill health forced her to resign in May 1874, but the next year she gained her first-class teaching certificate, which was the equivalent of a university degree. Brittan was appointed headmistress of the girls' division at Christchurch West School (now Hagley High School) in July 1875. Here she supervised staff, trained pupil-teachers and taught the higher standards. Her efforts were very successful and soon the school built up a reputation for scholastic excellence.
Thomas Foster was appointed headmaster of Christchurch West School in 1882, after teaching there as assistant master. On 29 August that year Emily Brittan married him at St Paul's Church, Papanui. They moved into the headmaster's house adjacent to the school. Unusually for the time, Emily Foster continued to teach even though she had three children over the next 10 years. Her life was full and busy with school, family, charitable work, reading and gardening.
After 19 years at Christchurch West School, Emily Foster applied for and gained the principalship of Christchurch Girls' High School, succeeding Helen Macmillan Brown in 1894. She made her personality felt at the school, but without making any radical changes to the existing system. She clearly believed that no field of study should be denied women, introducing classes in experimental science and Scripture, and annual school sports and school colours. Considering herself to be weak in mathematics, she worked to overcome this difficulty and made a point of teaching the subject. Her aim was to turn out girls who were not only successful scholastically, but also healthy, womanly and moral.
Emily Foster died suddenly on 30 December 1897 while visiting her brother-in-law at Rangiora, and was survived by her husband, two daughters and a son. She was well respected throughout Canterbury for her teaching abilities. Her partnership with Thomas Foster at Christchurch West School had made it one of the best primary schools in Canterbury. Her moral character, firmness yet kindness, guidance and friendship inspired those she taught. She was pale in complexion, with dark brown hair and soft brown eyes. Softly spoken, she had overcome a stammer. Her belief in Christianity developed early and was a strong influence and source of strength throughout her life.