At your school you may have decided that only the Loops administrator at your school has the authority to remove teachers from Loops. In that case you go to her/him for help. If you have the authority to do it yourself, you do it in the settings of your organization. Click the symbol for your organization, Administer participants and Teachers. In the list of teachers you click the name of a specific teacher and then you choose to Delete Account if that is what you wish to do.