Deleting your account is permanent and cannot be undone. When you delete your account, all of your Saved Games, Question Sets, Groups, Students and Student Data (if you enabled data collection) will be deleted along with the account itself.
To delete your account, log in to your account and then click on the person icon in the top right corner of the screen and then choose My Account.
Click on the red Delete Account button at the bottom of the My Account page.