Bullying as a child

Bullying is something that I (as most people do, I would think) have ZERO tolerance for. I have 5 kids of my own, and when I hear even the slightest bullying, teasing, or the like, no warnings are given and serious consequences are handed out right then and there. At home, my own kids respond to discipline well, (for the most part) are respectful, and are usually very kind to each other. In stark contrast, the majority of my students at school come from homes where teasing, bullying, etc. are tolerated. In addition, actions in this vein are ignored because parents don't have the energy, nor do they care, to enforce rules and discipline. So, when I come to school and see bullying going on left and right and I try to enforce rules and discipline, students think that they can walk all over me and that they can do whatever they want. Furthermore, there are so many kids that participate in this behavior that it is very difficult as a teacher to treat every case EVERY time it happens. With a class of 30 students, handling all offenses proves to be very challenging. HOWEVER, I do have on students who is a wonderful student and always tries her best. She is from Bangladesh. One day, a group of boys started picking on her class. I almost lost it! Let's just say, they KNEW right then and there not to mess with her again.