Germaine Bazzle, called New Orleans' "First Lady of Jazz," is in her element. And she is not, as one can often find her, at some popular nightclub singing on stage, flanked by first-class musicians and faced with an admiring audience.

Instead, she sits behind a wooden desk in her classroom at Xavier Prep High School, an all-girls school on Magazine Street. Bazzle's silver-and-black hair is slicked back. She waits quietly—her mood meditative—for students to arrive for the beginning piano co...