How Responsible Am I...

...for student conversations that take place in my room before the bell rings or during independent work-time?

I should preface with the following statement: I'm pretty sure high-schoolers have issues that are too big for me to know how to handle.

So I guess for the last couple of days a student in my class has been being threatened (in the way that high-school girls can do so well, but also is deeply concerning) by another of my students. The conversations took place before the bell one day while I was in the hall talking to students/another teacher and another day while I was taking roll/getting ready to start class. It left the threatened student very disturbed and has since been reported to a principal (whose diligence I'm not sure whether to feel secure about), so I am certainly not the primarily responsible party any longer.

In my generally powerful logical mind, I know that there is no way I can know what every student is talking about for each moment he or she is in my room. However, in light of a fellow intern's recent experience in the classroom, I am left very curious as to how much responsibility I have to each student in my room during the 48 minutes they are mine. When there are 30 warm bodies and desks smooshed into a space smaller than my living room, it is unlikely that I will make personal contact with each student or even get in many of their general vicinities.

Yet, as we strive to care for each student in our classes, we will automatically feel a certain level of responsibility for each of them. As teachers, we want our rooms to be a place where students feel comfortable and safe and when other students get in the way of that, what in the world are we to do?