I think there should be because teachers need to be watched to. Students could prank the teacher and no one will know who did it. People every day get away from stuff that happened in the classroom and then no one knows who did it or when they did it.
Of course not. Even students deserve a bit of privacy. Can't people respect that? It's definitely not fair for students to sit uncomfortably in their classrooms for hours every day knowing they are being watched by their teachers. They cannot do anything they wouldn't want anyone to see, and that doesn't include cheating. One or two teachers in a classroom are enough. No need for more.