ATL had members throughout England, Scotland, Wales, Northern Ireland, the Channel Islands, the Isle of Man, and British Service schools overseas.

All senior officers and officials were elected by an Association wide ballot and the overall direction was determined by the Annual Conference which had delegates from each branch.

However, in 1921, the AAM appointed representatives to the newly formed Burnham Committee on Salaries in Secondary Schools.

Between 1899 and 1908, it played an influential part in obtaining security of tenure for assistant teachers through the Endowed Schools Act.

Then in 1978 AAM and AMA merged to form the Assistant Masters and Mistresses Association (AMMA), with a membership of approximately 75,000.