One rainy Tuesday, the unthinkable happened. During a fire drill, the classroom was left unlocked. When the bell rang for the students to return, the desk drawer was hanging open like a Slack-jawed yawn. The Answer Key was gone.

The "thief" didn't last an hour. Leo, a first-chair cellist who had been struggling with his circle of fifths, walked up to the desk. He didn't have the book, but he had a confession: "We don't need the key, Mr. Henderson. We just didn't want to be wrong."

The Answer Key was found the next morning in the lost and found, tucked inside a tuba case. But for the rest of the year, it stayed in the drawer. Mr. Henderson realized he didn't need the book to teach, and the students realized they didn't need the answers—they just needed to hear the music.