Would the professor leave the classroom if only 1 student uses their cellphone during class? I’m a college student. My class has only 40 students. My professor left the classroom before class ended because, like he said, too many students were using phones while he was talking. It was not like there were phone sounds or the phones rang. He said before leaving that he would let us teach ourselves. 

In this case, I’m quite curious about something:


Would he be able or be allowed to not teach, and let us handle it ourselves and only come in to do the test?
Would he be able to fail the whole class?
Would he possibly react the same way if only 1 student used their phone without making any noise?
I've occasionally done "shocking" things to send an important message. It might be that all he intends is to make it a dramatic statement that you (the class) should take it more seriously. 

I doubt that he intends to not return, and also doubt that he would get any administrative support for that. 

I've always been willing to fail the entire class. Also willing to give full marks to the entire class. But that depends on individual, not group, behavior. Again, failing person A because of the actions of B would be unethical and would draw no administrative support. 

If it is only one student then, perhaps, a more nuanced and less dramatic response would probably be called for. 

In one of my "dramatic explosions" not every student was guilty. But even the ones who were more conscientious got an important message about proper behavior. In this case it was more about their own lack of preparation. There is a scene in Stand And Deliver in which the teacher, Jaime Escalante, denies entry to the classroom to a student who doesn't have his homework paper ready to turn in: "If you don't have a ticket, you don't get to watch the show."

But hopefully, the need for such drama is infrequent.