Johnston was a star basketball center at Savannah High from 1930-32, leading the team to three consecutive Georgia Interscholastic Athletic Association Championships. He also led the team to the Alonzo Staff Invitational Tournament in Chicago – where SHS represented Georgia in the 48-team tournament – making it as far as the quarterfinals. After his All-State career at SHS, Johnston played varsity basketball at Georgia Tech from 1936-38. While at Tech, he was named to several All-America teams and was selected as an All-Southeastern athlete. Johnson was the first basketball player to be inducted into Georgia Tech’s Hall of Fame.