[2][3] Jeffreys was educated at the University of Melbourne and first taught at a number of schools in Australia.
[1] In 1916, he joined the Australian Imperial Force, when he was an assistant teacher at Melbourne Grammar School, and in the Field Artillery Brigade that sailed for Europe in 1917 on the troopship HMAT (His Majesty's Australian Transport) Shropshire.
Jeffreys moved to England in 1921 to teach chemistry at Westminster School in London.
In 1928, Jeffreys founded Bryanston School as the "Master", with seven assistants and 23 boys aged between 13 and 16.
There was some friction with the governors, and Jeffreys resigned in 1931, taking up a post at Ottershaw College in Surrey.