login only registered users by admin

Hi
I want to create a login system without register option. that allow to users that registered by the admin to log in to the system. my system is private web to teachers in school, the school manager create a teacher profile and insert an email add/username (filed on the “teachers” collection) and after the the teacher can log in to the web. if the teacher does not exist on “teachers” collection, he can login.

https://support.wix.com/en/article/request-manually-setting-contacts-as-site-members