For our own good?

The other day, I was sitting in the hallway, laughing and chatting with my friends during a free period. I realized I had to call my mom to let her know I would be staying after school later, so I pulled out my phone and dialed without thinking twice. As I put the phone to my ear, I turned to my left and saw a teacher on hall duty glaring at me. "Are you kidding?" she hissed. "Put that away before I give you a Saturday school!" I could've been upset, I suppose, because it is my right to be able to call up my own mother! But it occurred to me then that the 'no phone call' rule was put in place at my school for a certain purpose. Not only would it be distracting for students to sit in the hallway and talk on their phones, but it could also be rude and overly casual.
As an American, I never really thought of my civil liberties as being infringed upon. America is always praised as the 'land of the free'. In school, we are not allowed to do certain things, but I realize that this is only to promote a safe school environment. I have acknowledged that, in certain situations, my liberties can be compromised.
With all this talk in AIS class of how much our liberties should be compromised during wartime, I think I see a real connection to the things I actually see in my every day life. I used to really be strongly opposed to limiting any Constitutional right, but I'm starting to see a different side. If students dressed inappropriately and said obscene things during class, I would obviously be distracted. We are not allowed to do these things because it would take away from a positive school environment. I wonder, is this the same thing we are seeing in wartime situations? I'm beginning to think the government should have the right to go against the Constitution in wartime, because, like in school, it's for our own good.