Crossing Borders...

Where do we draw the line, as educators, for students with a lack of what should be arguably already instilled "mannerisms?"  For example, I can recount numerous times where I had to directly teach several students how to act appropriately in public, how to speak to an individual of authority and adults, how to properly introduce oneself with a handshake, and even how to sit in the classroom... Needless to say, either I am justifiably compulsive with management in the classroom, or many of our students lack the ability to carry out "basic" functions in society!  Please, fill me in on this subject and enlighten me with what can be proposed to fix this dilemma, is it the teachers responsibility or the parents job?  Are we crossing over borders "illegally" so to speak when we correct and train students with what we, as educators, deem "appropriate behaviors."  One could justify that teachers have the right away because, "after all, they're teachers!"  But I counter that by testing this statement with what teachers find acceptable and unacceptable.  I've witnessed many varying opinions with teachers when it comes to, say, what our students can or cannot say in the classroom.  Curse words may be acceptable with Mr. A, but to Mrs. Z it might mean a week long detention!  Or what about uniformed schools who require students to tuck in their shirts, but many teachers fail to remain consistent with formal discipline by not enforcing it till the end or at all?