The America author Jack London was once a pupil at the Cole Grammar School in Oakland, California.
Each morning the class sang a song. When the Teacher noticed the Jack wouldn't sing, she sent him to the principal.
He returned to class with a note.
It said that he could be excused from singing, but he would have to write an easy every morning.
(The main idea is "Jack London's writing skill may be traced to his punishment in grammar school.")