Maybe we need a clarification by the OP:
— Is this about a teacher and students, and if so, students of what age? children? adults?
— Is this about teachers and the parents of students? If so, in what setting? In the classroom during class, in parent-teacher conferences, in a social setting?
Regardless, I still hold that within the classroom, which is the teacher’s domain, the teacher sets the rules and that it is no insult whatsoever to address someone politely and with respect, using a title, and to treat all alike. Likewise, in any extension of the teacher’s professional role, such as in a meeting with parents or a meeting that involves other teachers, the teacher’s rules persist. Outside that formal setting, social rules apply.
I think it is a typically American fault to apply social expectations to every kind of situation and relationship. Confusing business with social affairs is an especially annoying habit, resulting in parties where people try to sell you things and wedding invitations to the nuptials of the boss’s offspring. If a teacher is trying to model behavior appropriate to different situations, I say hurray.