Teachers can only be removed from Twine if they are not associated with any classes.
If a teacher is not associated with any classes, you may find their account under Users > User Info, and may use the Delete button to remove the account. The Delete button will not be displayed for teachers that are currently associated with classes:
To check whether a teacher is assigned to classes, you can log into Twine and use the Users > User Info menu to look up the account. On the Schedule tab you'll see any currently assigned classes:
To change the assigned teacher for a class, navigate to Scheduling > Courses and go to the course section that needs to be changed. You can re-assign the Teacher from there:
Once the staff member is no longer associated with classes you can go to the User Info page again, and should see the Delete button: