Personally, I think it depends a lot on the school, your country, and your co-teacher. I am student teaching at a high school right now in America and you are going to find all kinds of different students in your class so it is really hard to tell what kind of students you will get. I think as long as you communicate well with your co-teacher, show the students that you genuinely care about them, and have high expectations for them, you will be find. Your school will also probably have a discipline/classroom management plan for you and other teachers to follow so make sure to be familiar with that!
I hope this helps ease some of your anxiety. Middle school really isn't too bad haha!