The School Houses play an important role in Knox history and student life. It evolved gradually and by 1929 three Houses - North House, South House and School House (boarding) - were governed by their own prefects. A line through the suburb of Warrawee governed whether a boy was in South or North House but this line was later moved to Turramurra.
Gillespie House was formed in 1947 after the new dining room was completed and additional room was found in the Old MacKellar house.
In 1953, North House became Reid House, South House became McIlrath House and School House became MacNeil House.
Turnbull House was created in 1955; McKenzie, Murdoch and Ewan (Years 5-6 Learning Centre) were all introduced in 1970; Sinclair and Montgomery were the last to be added in 1977.
Each House is named after an historical figure at Knox.
John Adamson was a member and long-time chairman of the school council who devoted extensive time to the School.
(1955, disbanded in 1956 and reinstated in 1977) Professor the Rev Samuel Angus served on the Knox School Council, was a theology professor at the University of Sydney and president of the United Theological Faculty.
Dr William Bryden was second Headmaster of the School (1939-1953) in the difficult war years, during which time student numbers rose steadily.
(1970 senior boarding) Built in 1896 and purchased in 1928 to house the Preparatory School, it was named in tribute to the wife of Dr Armstrong, the house's owner who generously reduced its purchase price. In 1970 it became the residence for senior boarders.
Sir Robert Gillespie was a School founder, major benefactor and long-serving council chair. His financial acumen and generosity helped bring the school through the Depression and war years in a healthy state. His bequests include MacNeil House and the Old Preparatory School classroom block. His family members were also benefactors with a strong involvement in the School.
The Rev JJ Gilmore was a School Council member and a Presbyterian Church Minister. He was charged with finding the original site for the School and interested Sir Robert Gillespie and Andrew Reid in subscribing money to buy the property on which the School now stands. Since 2010, this House no longer exists, but is now a floor within the Boarding Centre opened in that year.
Neil H MacNeil was an Old Scotch Collegian from Melbourne and Knox's first Headmaster. He guided the School through its beginnings and the Depression, setting a strong tone and standard for the School.
William McIlrath was a founder and benefactor of the School and Council member 1923-1955. Respecting his wish to see a chapel built at the School, his widow offered 50,000 pounds to the School. It was built in 1960, containing a unique Baroque organ.
Dr T Ross McKenzie was Headmaster 1956-1969, a time of great consolidation and success for the School, particularly in terms of academic and cultural achievements.
J Ross Montgomery was a major School benefactor and council member 1953-1970. A civil engineering graduate and self-made man, he provided the School with the Montgomery building, Gilmore House, and numerous smaller benefactions including the bronze chapel doors.
AM Murdoch joined the School Council in 1938, serving as Chairman 1955-1969.
Andrew Reid was a founder and benefactor of the School. He became the sole proprietor of the firm James Hardie in 1912 after starting out as a bookkeeper. His numerous benefactions included the original Reid building, which contained a carpentry and metal workshop, art room, lecture theatre, armoury and storeroom.
George M Sinclair was a School Council Member from 1944, serving as chairman 1952-1955 and again as acting chair in 1969. An accountant and businessman, he chaired the council during a troubled period when the School's third Headmaster resigned after only 15 months in office.
Named after Alexander E Turnbull, a foundation member of the School council and an elder of St Margaret's, Turramurra. He was devoted to the interests of the School and for a long time was entrusted with checking the accounts for submission to the council for payment.