Joseph Firth was born in Wellington, New Zealand, on 25 March 1859, the son of Aaron Firth, a stonemason from the north of England, and his wife, Ann Priestnell. Gold fever took the family to Cobden on the West Coast and a scholarship took young Joseph to Nelson College in 1873.
Here by 1875 he was appointed a junior master under the pupil-teacher scheme; he coached football and cricket and played fullback for the college, and in 1879 he was captain in the college's cadet unit. He matured physically at a young age, and was a giant of a man at six feet five inches, who soon sported the neatly trimmed beard which he retained for the rest of his life.
When Joseph Mackay of Nelson was appointed headmaster of Wellington College in 1881, he brought young Firth over as a junior master; a number of pupils joined this migration, and Firth's influence did much to ensure their comfortable assimilation. He moved away in January 1886, to a post as gymnastics master at Christ's College, Christchurch, so that he could work for a BA at Canterbury College. He was active in theatrical and dramatic activities; but of greater importance was the influence of Professor John Macmillan Brown, who developed in Firth an appreciation of English literature and of precision in the writing and speaking of English that enriched his subsequent teaching career.
After graduating in 1889, on 8 May he married Janet McRae of Blairich station, Marlborough, at the Church of St Michael and All Angels, Christchurch. Two years later, on Mackay's resignation from Wellington College, the board approached Firth with a salary offer of £350 to become 'resident and boarding master and interim headmaster'; he accepted, and an association began which would bring dignity to man and school alike.
In previous years Wellington College had lurched from one crisis to another; a board of governors composed of otherwise distinguished citizens had failed to achieve financial stability, and all Firth's predecessors had left under difficult circumstances. Only 40 boys returned at the start of 1892, but another 50 arrived in response to Firth's appointment, such was his reputation already. The Wellington College old boys' record of 1891 had described him as 'undoubtedly the most popular master the College ever had.'
Firth arrived back at Wellington to find an insecure school community occupying a wooden building, Gothic Revival in style, amid rough grounds on a bleak hillside. These grounds soon gained his attention, with a fund-raising drive to improve playing fields and a weed-spraying wand of his own invention to keep the grass in good order. He was an active participant in the sporting life of the school for a number of years: in 1897 he bowled more overs than all other members of the school eleven. He was soon designated 'the Boss'.
Firth regarded boxing as a sport which encouraged boys to control their tempers (and after once losing his in the ring, he himself never boxed again). He believed in corporal punishment but his use of the cane was not indiscriminate, and he knew when admonition would achieve more.
Joseph Firth has been regarded as no great innovator in education, but he presided over great changes in the size and character of Wellington College, not least after the institution of free places in the Education Act 1904. His success in doing so made him the acknowledged leader in education in Wellington, and a respected authority throughout the country. His philosophy was simple: in his 1905 annual report he observed that it was not by being whipped that a boy could be made to do his best, 'but by causing him to look at his school life from the right point of view. This result depends very largely upon the parents' attitude towards the school and its masters'.
Janet Firth, an imposing woman almost six feet tall, was a tower of strength in the life of the school. Their marriage was childless, and the pupils (especially the boarders) were the extended family which substituted for the family they were denied. She took her place in the social life of Wellington, and dispensed gracious hospitality.
Although he had little time for organisations beyond the school, Firth involved himself in the Navy League, the National Defence League and as chairman of the Wellington Citizens' War Memorial Committee. The First World War took a heavy toll of his strength; more than 1,600 old boys of the college served overseas and Firth corresponded with almost all of them. His final year as headmaster opened with a roll of 678. When he retired at the end of 1920, 61 years of age but already in the grip of Parkinson's disease, he had become 'the old Boss'. His CMG in 1922 delighted him and the school.
The career as headmaster of T. R. Cresswell, Firth's successor at Wellington, was overshadowed by the legend – and at a multitude of school occasions, the presence – of Joseph Firth. In 1924 he was able to open the new boarding establishment, Firth House; but by 1928 he was too frail to speak at the opening of the Wellington College Old Boys' War Memorial Hall which he had first proposed a decade earlier. He died at Wellington on 13 April 1931; his wife died on 6 August 1939.
We must allow that Firth was not devoid of vanity: his teaching of the vicissitudes of the Spanish armada in its passage round the north of Scotland gained him the nickname of 'Pentland' Firth; thereafter he signed himself 'J. P. Firth'. But he inspired a generation of boys, and that is no small achievement.