A classroom environment that is managed well, where students understand what is expected of them, have clear routines and follow classroom rules and procedures, is a prerequisite for effective learning. Learning happens when students are curious, focused, interested, and engaged; disruptions happen when they are bored, confused, or struggling to keep up.
Creating a positive learning environment of mutual respect, where students feel safe and able to take risks, allows fruitful exploration of ideas and effective learning to take place.
Conversely, poor classroom management wastes so much time. If a teacher feels like they get to the end of every lesson having covered only half of the things that they set out to, it is probably down to their classroom management techniques.
So, in order to be more efficient in class, in order to cover all the material that they would like to, a focus on classroom management techniques might be their saving grace.