The first official unit in Australia was established on 29 March 1866 at St Mark's Collegiate School by Reverend Macarthur.
In June 1868, The King's School had closed and did not reopen until January 1869, when it was amalgamated with the St Mark's unit, the unit was renamed The King's School Cadets Corps.
Once enrolled, they may remain as a cadet until the day before they attain the age of twenty years.
A cadet in the AAC is not considered to be a member of the Australian Defence Force, nor are cadets allowed to be a member of the Defence Force or, other than in approved exceptional circumstances, any other cadet service during their time as a cadet.
In 1975, the AAC was disbanded by the Whitlam Labor government and was re-raised by the Fraser Liberal government on 1 October 1976. As a result of the Beazley Defence review white paper in 1984, full military support was withdrawn from school based cadet units, now classed as Limited Support Units (LSU).
Military support for LSUs was limited solely to the discretionary loan of equipment for Annual camps.
Officers came from teaching staff and selected cadets were made "Cadet Lieutenants".
In 1939, the outbreak of World War II caused the Regimental Detachments to be disbanded as staff were needed to train soldiers for overseas service.
With the establishment of many cadet units and corps at numerous boys schools throughout the Commonwealth, His Majesty King Edward VII established the Commonwealth Cadet Corps in Australia on 16 July 1906.The Duke of Edinburgh presented his banner as a gift to the Corps on at Victoria Barracks, Sydney.At this time, there were 46,000 cadets in Australia.The Australian Army Cadets (AAC) is a youth organisation that is involved in training and adventurous activities in a military setting.The programme has more than 19,000 Army Cadets between the ages of 12½ and 19 based in 237 units around Australia.