Anyone with Super Admin or District Super Admin access can change the access level of a staff account or delete the account.
To do this, select Settings to see a list of all of the users at your school or district, broken down by current access level.
Click the settings icon to the right of a user's email address to edit their account. Select "Change Role" to set their new role using a drop-down menu. If you select "No Access", they will be removed from ST Math. Removing access to an educator's account where they are tied to a class, will have an Inactive label next to their name.
If you need to restore access to a teacher you've removed, just use the 'Add' button add them back in! (How do I add new staff accounts?)
See also: What are the different access levels for staff accounts?