If you are using LessonUp classes
Go to 'My Classes' and select the class that the lesson has been shared with by double clicking on it or using the yellow 'Lesson results' button on the right side of the screen. Then select the lesson. In the column on the right side of the screen there is now the option 'Delete'.
When you click on 'Delete' you will see a popup screen with two options: 'Remove only from My LessonUp. Students keep their shared lesson and progress' and: 'Remove from My LessonUp and the app of ... student. Student progress will also be removed'.
Choose the desired option. The lesson has been deleted. The removal cannot be undone.
If you do not use LessonUp classes
Go to the original lesson you shared in LessonUp. Select the lesson and on the right side click 'Share with students'. In the screen that appears choose the shared lesson you want to delete and click on the trash can.
When you click on the trash can, you will be presented with a popup screen containing two options: 'Remove only from My LessonUp. Students keep their shared lesson and progress' and: 'Remove from My LessonUp and the app of ... student. Student progress will also be removed'.
Choose the desired option. The lesson has been deleted. The removal cannot be undone.
Good to know: you are deleting the shared lesson (the copy), not the original. Reports are deleted.