How do I give organisations the chance to offer their members premium content?

Hello all

I’d like to give language schools the chance to pay a fee and offer their students access to premium content on my WordPress site. We’re probably talking about from 20 to 200 students for each school. What is the easiest way of achieving this? I see that there are dozens of membership plugins but have no idea whether any of them offer this kind of functionality. I had considered the possibility of introducing a “Premium” category, password-protecting it and sending the schools a new password every two weeks or so for them to give to their students. Is there any way of selling a “package” of memberships (say 100)?

I’d be very grateful for any help/suggestions offered!