If everyone is cheating and you expel them all, there will be no one left.
A far better approach for this professor would be to use a tool like RevisionHistory.com
Itâ(TM)s a totally free chrome plugin that gives stats on how a document was constructed, by analyzing the revision history. It will tell you how many copy/pastes there were, the size of them, and will even let the user to do a âoereplayâ to watch the document being written at high speed to help understand the student process. The student does not need to install anything, but merely needs to use a Google Doc to write their essay and when done, share it with the instructor.
Students will cheat, unless they expect to get caught.
The best penalty is a zero grade with an opportunity to do it over.