This is over the line! I was never fond of the times I was video taped in my classroom but I learned a lot about my teaching and my kids from watching the tapes. Always-on web cams are a different story. The purpose in this particular instance is to improve discipline but that’s never where this kind of experience ends. Everytime a teacher strays from the script, some parent somewhere will object. Even though every good teacher knows that going off topic once in a while can often lead to some very good learning.
By all means put cameras in the classrooms of teachers who are under serious suspicion of incompetence or misbehavior. Principals need these kinds of tools to make it easier for them to fire bad teachers. At some point, however, we have got to give teachers good support and training and then trust them to do a good job.