How do I delete a class?
On your main dashboard, click on the gear icon on the top right of that classroom "box" and select Delete classroom. Beware that any student in that classroom will also be removed from your tracking list. If you wish to keep them, please move them to a different classroom first. More information on our Help page under "How can I modify classrooms?". :]
It's been a while since this original answer and it looks like it might have changed a little. Currently, if you click the gear icon on your classroom there should be an option to go to "Classroom Settings" then click the "Delete this classroom" link at the bottom of the settings page.