Beside students your school also has administrative staff members, teachers etc. And you have to create them from your school settings.
From the main dashboard in the top right corner click on the Settings button.
Choose the Members tab and click on the Create button.
Then the member create form will pop up. Fill all required fields and choose the role of your member such as manager, teacher etc. Later they can sign in to LMS with the credentials you have created.
Here you can also edit, delete your school members.
Submit and you will see a new member in your list.