Since I began teaching last September, I've had one class in particular that has been giving me and their other teachers some grief. Even experienced teachers have had to walk out of classes in which they were completely unmanageable. Fortunately, it was months before I realized that was even an option otherwise I would've probably left the first week. Not knowing that has forced me to learn other classroom management techniques. Basically, I learned how to enter comments into the computer and gradually build up a case of how particular students are ruining a class.
Furthermore, I've been conferring with this class's other teachers and we've been writing comments and sending the students' supervisor mails telling them about the situation. While it is virtually impossible to get students removed from school for anything apart from poor attendance, our efforts have had the effect of having the three worst offenders of that class split up and transferred into other classes. The initial reaction would be to say, "Great, now you have four bad classes instead of one." As it turns out, once the students are isolated and on their own, they tend to settle down. Plus, it has the added bonus of pissing off the offenders.
I have to say that this was only possible because of the great support we have from the supervisors in our school. I've heard that it's not always the case in other schools.