Here is the email I’m going with, is this too far?
“Hello,
I wanted to let you all know that I will no longer be working for _____. It has been made clear that I am replaceable, so I will no longer be a part of a workplace that treats people in a way that the staff here are treated.
I am not referring to only today or only myself. You have some very hard working staff who are treated so poorly that it is honestly shocking.
I am leaving effective immediately as I do not feel the need to show professional courtesy, if I am not in turn shown human decency.
I know the content of this email will likely be written off as the words of a disgruntled employee, but I encourage you to look further. Your employees are good people, and they deserve an upper management who treats them with respect and decency.
I have left detailed notes on my desktop of what needs to be done for my assigned classes.”