Custom Capability - Allow schools to bulk create new users

I sell annual school subscriptions giving access to eBooks as web apps, hosted on my WP site. I want one or more staff members of the school to be able to add and manage users - every teacher and student in the school will require access. I would prefer not to have to manage this process myself. I imagine the easiest way would be to be able to upload a csv file with first name, second name, email address. I only want the school staff member to have access to this custom capability for as long as their subscription is active, and for the users they create to have access to the web apps for as long as the school subscription is active. I think maybe I can figure out how to give promote_users custom capability, but there’s an added complication. I only want the staff member to be able to manage users within their school community; not for all users from all subscribed schools. Help please!