Sure, our marking can be pretty easy in the sense that when exam time comes around we are not usually swamped with 90+ exams to mark because most of our exams are performance-based. But while our marking is easy, our profession make up for that in how hard it is to run the class. In a regular classroom you have desks and chairs and a chalkboard (or whiteboard) and the students are conditioned to sit. You can move students around if they can't be near each other. You can make one face the wall. You can even place a kid in a desk outside. In drama you have an open class room with no desks or chairs and sometimes there are props and other things students can get their hands on to 'play with'. It's been compared to a lot of things: herding cats, a war zone, a jungle. My comparison at the moment is that high school is like prison.
In prison (at least stereotypically I haven't had the opportunity yet to stay in prison to get an accurate depiction of the place) you have your cells where the inmates spend most of their days. They're small, confined, and the prisoners are generally well behaved. The cells are like the 'academic' subjects. Math, English, Science - anywhere that there's a structured environment.
When the bell rings, it's the same as when prisoners move to the cafeteria or for showers or to work. There's chances here of something going wrong, but it's kept to a minimum because there's a lot of teachers/prison guards around. Even the cafeteria is the same since every day there's the worry/threat of a fight breaking out and how will or won't sit at your table while you eat. Sometimes the students (inmates) even question the cafeteria food and if you're lucky your favourite relative sent you a care package of cookies that you can eat or share with your enemy that you need to make friends with.
And then there's Drama. Drama is like the free-time yard in prison. It's an under-staffed confined space where you can roam around and interact with anyone you please. You know that guy who's really annoying to you every other class? That girl who wrote something mean on your Facebook wall? Now's the time to get revenge. If you want to "shank" someone, it'll be in drama. And if you're smart about it, you'll do it within the confines of a drama activity so the prison guard (teacher) has a hard time disciplining you for it.
It's hard as a teacher to always see this coming. Sometimes you do and you can be all over the situation before it develops into something more and sometimes, much like a prison guard, you get distracted by something over to the left and then the people to the right take full advantage and make their move.
Now it's not always like this, but sometimes it can feel like it is. I'm sure some students feel the same way, too. There's not a lot that can be done about it. You throw enough adolescences into the same place and make them put up with each other, you're bound to have some issues.