I had two student teaching placements during my credential program (I just finished last month), and the first was in 6th grade. It was a self-contained class at the elementary level - in my state, 6th grade can be elementary or middle school, depending on the district. I was VERY nervous going into that placement - I had always said that I'd be happy with any grade..except for 6th! haha. I had experience with the little ones, but I'd also taught a 4th/5th grade combo class in an after school program for 2 years, so it wasn't SUCH a huge jump - although 6th graders are a LOT different than 4th graders.
Despite my initial disappointment and nervousness, it ended up being a great experience. I had an excellent cooperating teacher, for one thing - that always makes the difference! Also, the kids and I really warmed up to each other. I really loved being able to have deeper, more meaningful discussions with them. It took awhile for them to warm up to me...it's not like 1st graders who love you after 5 minutes
...but once they did, they were extremely loyal. I got lots of hugs and notes. I really was able to develop great relationships with the kids. The thing I liked best about 6th grade is that they are REALLY able to step up and begin to take responsibility for their own learning. They are also able to take on leadership roles, in and out of the classroom.
6th graders need CONSISTENT expectations and rules. They also NEED their teacher to be fair - and they will instantly notice the moment something is not fair. Management can be tough with 6th graders, because they like to push the limits - but they do respond to consistent expectations. They are old enough to understand that there are consequences to their actions, and if those consequences are given out fairly, they will accept them.
I think you may find that you like 6th grade more than you'd think.
I'm so glad I was placed in that grade level - I loved the kids and it really gave me a lot more confidence - before that experience, I never thought I could teach 6th, but now I know I could.
Best of luck to you! Enjoy your experience!