The janitor knows more about your character than your teachers do. He sees what you leave behind.

Teachers see the version of you that is being assessed. Whoever cleans the room afterwards sees the version that was not thinking about anybody, and that is where the real information lives. What you leave behind is a message you did not know you were writing, addressed to somebody you never pictured. Almost nobody considers that audience.

Pick up your own mess, including the small things nobody saw you drop. Say hello to the person cleaning, by name if you know it. If you do not know it, that is easy to fix this week.