Restrict access to a new schema to a specific role despite users having db_datareader?

I’m working in a SQL Server 2016 database that is not of my design nor can I fundamentally change the security structure. I know it is likely trash/worst practice but I have to play the hand I am dealt at the moment. I’m trying to restrict access to a schema to only members of a role, but everyone seems to have db_datareader membership. Here are the details:

What is the “wheel” user in OS X?

I recently reinstalled iTunes and I noticed something peculiar. The “original” version of iTunes has a user in the permissions known as “wheel” that is set to “Read Only”. I dragged this version of iTunes to the trash and installed a new copy, and when I look at the properties for iTunes it no longer says wheel, but rather just admin.