Tricky Models/Associations problem

I have a User model and a Teacher model that inherits from the User model.

The User table has a column called :admin with a boolean value. This allows me to set any User as an admin (via the Rails console: 'User.find.(2).update_attributes(admin: true)'.

I want to create a Materials model.

This would be simple if it was only relevant to, say, just Teachers. I would then have a simple Teachers has_many :materials and Materials belongs_to :teacher.

However, I want any admin to access and post to a 'master' Materials page...

...and I want each Teacher to have their own 'Materials' page that they can post to AND....

I want Teachers to be able to go to the 'master' Materials page and select Materials from that page to also appear on their own Materials page.

After much deliberation, I think I need to have Materials has_many_and_belongs_to :users and ALSO belongs_to :user.

I'm not sure how to go about this, but I think something like this might be a solution: http://stackoverflow.com/questions/13959955/belongs-to-and-has-and-belongs-to-many-to-the-same-table-in-rails

Am I barking up the wrong tree? What do you think?

Might need a staff to help me on this one? Jason Seifer ?

Another potentially tricky aspect, is that I would want all the Materials on a Teacher's Materials page to be listed chronologically (by date of creation), even when that list contains Materials from the Admins' Materials page.