Stafford's first public singing appearance was in Long Beach, where the family lived when she was 12. She sang "Believe Me If All Those Endearing Young Charms", a Stafford family sentimental favorite. Her second was far more dramatic. As a student at Long Beach Polytechnic High School with the lead in the school musical, she was rehearsing on stage when the 1933 Long Beach earthquake destroyed part of the school. With her mother's encouragement, Stafford originally planned to become an opera singer and studied voice as a child, taking private lessons from Foster Rucker, an announcer on California radio station KNX. Because of the Great Depression, she abandoned that idea and joined her older sisters Christine and Pauline in a popular vocal group the Stafford Sisters. The two older Staffords were already part of a trio with an unrelated third member when the act got a big booking at Long Beach's West Coast Theater. Pauline was too ill to perform, and Jo was drafted in to take her place so they could keep the engagement. She asked her glee club teacher for a week's absence from school, saying her mother needed her at home, and this was granted. The performance was a success, and Jo became a permanent member of the group.