Hi,
I think that in your case, the switch user add-on could be a solution.
It will add a dropdown for some roles (staff, teachers, etc…), and allow the currently connected user to switch the dashboard view to the one of someone else, just to see the posts.
However, it won’t be a solution if you also want teachers to interact (eg modify, add files) with other teacher’s contents.
In this case, I would recommend to auto-assign all the contents posted by the student to a group that includes all the teachers. The problem, in this case, is that all the teachers will receive the notifications from other students, and that can be annoying.
I’ll ask @vprat if he has a better solution for this.