Security and privacy

We would like our teachers to have access to all of the other teacher's courses. Enabling Guest Access for the entire site worked but it also meant that our students would also have access to all of the courses as well. We have well over 100 courses that start every three weeks so managing it at the course level would be impossible. I tried to figure out a way to create a system role that would grant site wide guest access thinking it would be easier to manage one list than all of the courses. I didn't really get anywhere with that. Any creative solutions? Thanks!