Janet Craig McKutcheon Mackenzie was born in Edinburgh, Scotland, on 3 July 1878 to James Hutton Mackenzie, a divinity student, and his wife, Janet Craig McKutcheon, who died of puerperal fever 11 days later. After the death of his wife, James Mackenzie abandoned his plan of working as a missionary in China and in 1880 emigrated to New Zealand with his young daughter.
Janet presumably lived with him in Southland, where he was inducted to the Presbyterian church in Wallacetown in 1881. James Mackenzie moved in 1889 to St John's Presbyterian Church in Lyttelton, and the following year married Charlotte Elizabeth Johnston. From this marriage Janet gained four half-sisters and a half-brother, who died young.
Nothing is known of Janet's early education but she attended Nelson College for Girls in 1892, 1893 and possibly early 1894. Her teaching career began in Nelson, where her family had been living for some years. She worked as a pupil-teacher at Toitoi Valley School (1897–98), beginning on a salary of £18, then at Haven Road School (1899). As a full teacher she taught at Aniseed Valley School (1905), and at Nelson Girls' Central School (1906–9). In 1913 she left the Nelson area and began teaching at Raumati School. Her last appointment was to Waipawa District High School in 1920, at a salary of £280.
In 1922 Janet Mackenzie's career underwent a decisive change with the introduction by the Department of Education of a system of teaching children by correspondence. In late 1921 she responded to an advertisement for a teacher, preferably female, to be paid a salary of £240–£270. Mackenzie, by this time an experienced and capable teacher, was appointed. Working from the Government Buildings in Wellington, her task was to cater for the needs of 83 children, many of whom could neither read nor write, and who ranged from beginners to standard six. She took up her duties under the Correspondence Scheme (later Correspondence Classes) on 1 February 1922.
In the very early days she had no assistance at all. She later wrote that 'there was nothing then of the school you know. Nothing. Not even a room. Nothing but a pile of application forms, and a teacher with a pen'. There was also no library, no magazine, no opportunity for her to visit her pupils. The numbers of children receiving this education increased quickly, with 300 enrolled and another teacher appointed as her assistant by the end of the first year. Some clerical help was soon provided, but the two women still worked until late at night and on Saturdays to keep pace with the vast numbers of letters that had to be sent to pupils and the heavy load of marking on which the system depended. All instructions, explanations, corrections and words of encouragement, as well as letters to parents, were written by hand.
With her experience in small country schools, Janet Mackenzie was well qualified to give pupils individual attention and she was completely up to date in her approach to teaching English. The lessons were devised to be done every two weeks. The use of simple, direct language was emphasised and creative writing was strongly encouraged. Her lively and exuberant personality, wit and love of literature overflowed into her work.
The success of correspondence teaching encouraged the department to extend the system by appointing a headmaster in 1923. Janet Mackenzie, who had devised and implemented an excellent and imaginative programme, became the first assistant. The new headmaster continued with Janet's framework and she gave him and the students her best work. During the following five years she wrote a number of graded English textbooks for pupils in standards one to six. These books, part of a departmental policy to provide textbooks for the nation's schools, were used until the 1940s.
When she retired from the Correspondence School in December 1931, its magazine noted that 'in her departure the school loses one of its most ardent supporters'. She continued to live in Wellington until 1938, when she went on holiday to Scotland. Her visit, intended to last for one year, was extended by the outbreak of the Second World War. She became involved in war work such as helping in canteens, and returned to New Zealand seven years later. Janet Mackenzie lived out the rest of her life in Wellington until her death there on 14 July 1962.