Good discipline does not necessarily mean that you can hear a pin drop at any given moment. Sometimes people stereotype good behavior as something that is super serious, low energy, and robotic. This does not have to be the case. All that really matters for successful discipline to be taking place is that nothing happens that the person in charge does not allow. If that means consistent quiet, then fine. On the other hand, if the person in charge has no problem with a little noise or conversation, then that is fine too. I am usually somewhere in between these two extremes, depending on what is taking place. The key idea here is that the person in charge has the power to decide!
Teachers who want to be successful simply need to figure out what they want to allow and not allow, and develop a plan to enforce those expectations.