Adamson started his professional career as a pupil teacher at a Church school in Marylebone. In 1876 he went to St. Paul's College, Cheltenham. There he obtained his teacher's certificate. He then taught in London and became second master of the Great College Street Board School. During this period he took an Arts course as an evening student at King's College London. He gave most of his attention to a study of Latin and Greek. In 1881 he graduated. In 1890 he returned to King's College as the first head of the training department for teachers.
Professor at King's College
Between 1890 and 1924 Adamson held the following positions at King's College:
The Department for the Training of Teachers of King's College was established under John William Adamson in October 1890. In 1896 it was split into two sections: the 'Day Training College' for those intending to teach in elementary schools, and the 'Department for Secondary Training'. These were amalgamated in 1922 to form the Education Department, part of the Faculty of Arts. This became the Faculty of Education in 1968, which merged with the Chelsea College Centre for Science and Mathematics Education in 1985 to create the current School of Education. King's College London was one of the first institutions of university rank to open a 'Day Training College.' This became the direct ancestor of the modern university department of education, which still fulfils the double purpose of training teachers, and also to foster the academic study of education and research in this subject. October 1890 one of the former students of King's College London, John William Adamson, was appointed to be head of the training department and 'normal master'. "His duties were 'to give lectures on the history and theory of Education, to superintentd the students' work in the practising school, and to give a course of model lessons and preside at the criticism lesson'. There had been forty applications for the post and seven candidates were interviewed. It was a condition of appointment that, in accordance with the charter of King's College, applicants should be members of the Church of England and make a declaration to that effect. The annual salary attached to the post was fixed at £180." The earliest history of the department can be followed in the logbook which Adamson kept and which is still preserved at King's College. Already in 1897 almost the whole of the Faculty of Arts at King's College was formed by 'Education' students.
In 1900 a Board of Studies in Pedagogy was formed, of which Adamson became the secretary, and later chairman. Adamson's role was further recognized by his appointment as lecturer in 1901 and as professor in 1903.
Other functions
Other functions of Adamson were:
1909-1910: President of the Teachers' Training Association.