Well, it is very common in situations like this to have 2 to 4 assistants, and I can't believe without them it would be possible to avoid hard conflicts and even violence on regular basis.
She has no assistants and never has (I just asked her). Occasionally a student teacher but not for years, now. Some students, such as ESL or special ed, are pulled out of class for about 30 minutes from 2–4 times a week but, the recent district policy is called "push in" where the specialist comes in to class to assist a particular student or two.
Where are you basing this on? In public schools in the US (at least in my hometown in Louisiana), schoolteachers don't get assistants of any sort. You get the occasional "student teacher," who is training to become a schoolteacher, but never more than one.
Faculty at colleges get teaching assistants, but their job is hardly to help with conflicts or prevent violence, their job is to help with instruction, grading, writing homework assignments, etc. When I was a teaching assistant, I myself tended to have 10-20 students in my section, and the class as a whole had close to a hundred people.
I'm most familiar with China (I taught middle-school classrooms of 55-60 in Yunnan around 2010, and had some friends in Guangzhou teaching 75-80), but I assume there have been & are plenty of countries with similar situations.
