At the outbreak of World War I he served as a bomber pilot with the Second Oxford Detachment of the British Royal Air Force.

In Paris, Lavalle studied at the Académie Julian as a pupil of Jean-Francis Aubertin.

Upon returning to the US he enrolled at the School of the Boston Museum of Fine Arts, going on to establish himself as a successful painter of society portraits throughout the 1920s and 30s.

When the US entered World War II Lavalle served as a camouflage artist for the 12th Air Force prior to the invasion of Sicily, and painted many portraits and combat scenes of its subsequent campaigns.

After World War II, Lavalle moved from Boston to New York where he painted numerous portraits of various eminent academics.