I don't know how many times I have had to hush my children so that I could finish giving directions. They are so eager and wanting to ask questions, before I have finished talking myself. They have to be taught expectations of behavior along with discipline. I think having good manners in the classroom is beneficial to everyone in the classroom and allows for the lesson to run smoothly. I feel in the long run, children who are taught manners will have a great advantage when it comes to acting and behaving around other people.
Good manners allow for good communication and also coincides with good discipline.
They speak to their teachers the same way that they speak to their peers. I'm glad you're making it a priority to instill these manners and demand they be used in your classroom. Most children may be from a home where this is not practiced so they don't know any different. Be a good role model and help to promote what you believe will make them better people. Hopefully they won't fight you on it and will practice good manners in their life, both at home and at school.