O'Malley attended Jamaica High School in Queens from 1918 to 1920 and then the Culver Academy (the eventual high school alma mater of future New York Yankees owner George Steinbrenner) in Indiana. He managed both the baseball and tennis teams, served on the executive staff of the student newspaper, was a member of the Hospital Visitation Committee as well as the debate team, Bible Discipline Committee and the YMCA. At Culver, his baseball career was ended with a baseball that hit him on the nose.