Blackmailed by one of your students

One Friday, Rebecca Jennings made her way to work. She was a Calculus teacher at a prestigious private high school. She loved her job, and she loved her students.

Today, she was giving a surprise pop quiz. Luckily, her students took it pretty well.

For most of the shift, she simply sat at her computer and composed another assignment for next week.

Over the course of the next forty-five minutes, her students turned in their quizzes. Soon enough, all but one of them had finished.

The last one was David Taylor, which struck Rebecca as odd. David was her top student, usually among the first done with assignments.

He managed to turn his assignment in just before the bell ring. However, Rebecca noted that he had turned in another piece of paper alongside his quiz. Rebecca curiously opened it up, and it said, "I want to talk with you during lunch."