I can understand that teachers get frustrated with kids. I personally have seen it and been a part of it as a kid myself. I have watched my fellow classmates push a teacher to the brink, and caused that teacher to lash out, and I have known teachers to lose it and cry and have emotional breakdowns.
But I will never condone a teacher lashing out at kids. Not in any way, shape, or form. The fact that this teacher did it in this manner makes it even worse, but frankly I don't care if she called them little shits or morons or worthless or whatever. It's never okay. It violates the teacher/student relationship. The job of the teacher is to inspire the kids. Educate them, earn their trust, and sometimes take the hit. Kids are ruthless. If you can't handle it, don't become a teacher. It's that simple.
With that said, our education system needs a huge overhaul. Our children are not getting a good education, and it's not the fault of the teachers. The system is broken. Plain and simple, and the teachers are on the front lines of that failure, but it is never okay for them to take out their frustrations on the kids. Never. Period. End of discussion. This kind of attitude can not be allowed.