The first edition of the Knox yearbook, The Grammarian, in 1928 provided an explanation of our School motto.
"The motto (of Knox) consisted of two words Virile Agitur and the School will bear this motto until it shall be time honoured and hallowed among Old Boys and present boys alike. The spirit of the School is denoted by its motto, and therefore the spirit of our School is "The Manful thing is being done". The motto presents our object for every boy; he must see to it that he is doing "the Manful thing", the right thing. We must always follow our motto, and by doing that we will benefit not only ourselves but our School, and in later life, our State, Country and perhaps the World."
Under founding Headmaster Neil MacNeil, a Rhodes Scholar, Knox grew rapidly both in academic achievement and by providing students with practical skills in areas like woodwork and metalwork. Knox survived the Great Depression with expanded facilities. Student numbers rose from 28 in 1924 to over 300 in 1939.
In 1939, MacNeil was succeeded by biologist Dr William Bryden. As WWII broke out, around 680 Old Knox Grammarians served in the armed forces. Sadly, 68 of them lost their lives and are now commemorated in the School Chapel, Old Students' War Memorial, the John Williams Memorial Hall and the original Science Building (now Art).
Despite this difficult time, Headmaster Bryden oversaw considerable growth in the School's academic standing and an expansion of facilities in the 1940s and early 1950s. It was also during this time the Pipe Band was established.
Bryden’s successor in 1954 was Dr John Mill Couper, a Scot, who broadened the School's concept of education, with particular attention to music and art. It was during his headmastership that the House system we recognise today began to develop.
The problems were short-lived and the next Headmaster, Dr T Ross McKenzie, provided the vision and down-to-earth management style that brought Knox to the top echelon of independent schools. A long period of steady growth and firm leadership followed and by Dr McKenzie's retirement in 1969, the pursuit of excellence had been realised in many of the School's endeavours.
The next Headmaster, Dr Ian Paterson, AM, initiated further significant developments including a substantial building program, an outdoor education program, the introduction of a wider selection of sporting choices beginning with basketball and soccer/football, and the introduction of the school musical. During this era, Visual Arts, Music and Drama entered the NSW syllabus and the appointment of specialist staff strengthened and anchored the development of the creative arts. In 1974, the school turned 50 years old. There were more changes to come before the 21st Century arrived. The Music Centre, Lawson Centre, Reid Industrial Arts Building, Paterson Centre and the purchase and building of the Grahame Mapp Oval and the Gifford Pavilion in North Turramurra are some of the major projects completed in this era.
In 1999, Peter Crawley, former Head of Trinity Grammar School in Melbourne, became Knox's sixth Headmaster, bringing the School into the 21st century with an innovative program of technology and computer-based learning. He oversaw steady improvements to student life and retired from the School in 2003.
The seventh Headmaster, John Weeks, joined Knox for the start of the 2004 school year from The Illawarra Grammar School. He brings to Knox strong educational and leadership experience and an empathy and understanding of working in partnership with School communities.
Today there are about 2,400 boys at Knox, with more than 1,800 in the Senior School and 600 in the Preparatory School. Knox also operates Wahroonga Prep, a co-educational campus for girls and boys from Pre-Kindergarten to Year 6. The School offers boarding for up to 200 boys from Year 7 onwards. The School has a teaching staff of more than 200 with additional staff employed in roles such as visiting music, physical education, information resource teachers and ancillary support.