William John Cooper taught high school social studies from 1907 to 1910 before working for the US War Department from 1918 to 1919.
He began his career as a high school teacher of Latin and History in Stockton, California from 1907 to 1910, then directed history teaching in Berkeley, California for four junior high schools and one senior high school, as head of the Department of History of Berkeley High School from 1910 to 1915. He worked for the US War Department for eighth months from 1918 to 1919 in education and training. 
