What does the following paragraph mainly reveal about Marian Anderson?
"While she dreamed of a singing career, she knew she would have to support herself and help her family when she finished school, so she took the high school’s secretarial course, studying bookkeeping, shorthand, and typing. But her heart wasn’t in those studies, and after three unhappy years she was able to transfer to the newly established South Philadelphia High School for Girls, where she enrolled in an academic course, emphasizing music. Her classmates would remember her as a shy and often self-conscious young woman who kept to herself and concentrated on her musical studies."