Resetting a Course
If you are teaching the same course for a second semester you can easily remove all students and student data associated with that course. In the Administration block click the "Reset" link. This takes you to a page where you can select what to remove from the course. The General section allows you to change the Course start date and delete course events, logs or notes you have created.
The Roles section lets you delete students, non-editing teachers, or guests. The Gradebook section will allow you to "Delete all grades" from current students. If you choose to not "Delete all items and categories" they will remain for you to use for the new semester. In order to remove all traces of students from previous semester select the following: "Delete all submissions" under Assignments; "Remove all messages" under Chats; "Remove all responses" under Choices; "Delete any entries by students not enrolled" under Databases; "Delete all posts" under Forums; "Delete any entries by students not enrolled", "Delete all ratings" and "Delete all comments" under Glossaries. This will maintain all content created by you, while eliminating all content created by students.
Click the "Reset course" button at the bottom and Moodle will show us a page with all the deletions it is about to make. Click the "Continue" button and you will see the main page of your Moodle course. To check that all user data has been removed click the "Participants" link in the upper left hand corner. The only participant should be you.