In 2015, his freshman year at Lafayette High School, Duplantis set national freshman records both indoors and outdoors and was named Gatorade Louisiana Boys Track &amp; Field Athlete of the Year. As a citizen of both the United States and Sweden, Duplantis could have chosen to vault for either country internationally; in June 2015 it was announced that he had selected Sweden. Duplantis represented Sweden for the first time at the 2015 World Youth Championships in Cali, Colombia; he won gold on countback with a first-attempt clearance of 5.30 m (17 ft  in), improving his personal best by two centimeters and setting a new championship record.