A student might request to have his/her progress reset because they intend to take a course again, or for another reason. You cannot reset progress, but you can make sure all attempts prior to a certain date (the starting date of the class) are ignored.
To set the start date of the class, go to Teacher > tab Settings and then choose the time period that you want to count in.
Specifying and end date is optional. Note that if you also specify an end date, students can no longer record their progress after that date.