Until the Second World War, the congress of this league included a number of other teachers which were Maria Montessori, Célestin Freinet, Gisèle de Failly and Roger Cousinet.

He worked as a humanist and an editor from 1919 to 1922 on the pacifist journal 'l'Essor' (The Rise).

[1] In 1924, alongside his colleague Paul Meyhoffer from the Institut Jean-Jacques Rousseau, and the League of Nations officials Arthur Sweetser and Ludwik Rajchman, Ferrière founded the International School of Geneva (the first of its kind in the world) and, during the early months of its existence, provided the new school with accommodation in a chalet he owned.

[2][3][1] He was one of the founding members of the International Bureau of Education (IBE) in 1925, and served as its first Deputy Director alongside Elisabeth Rotten.

[1][5] Throughout his life he published a substantial number of books, some in collaboration with Karl-Ernst Krafft.