I'm a teacher, too, though currently on leave, and I always found that punishment in classrooms never works anyway - the kids who get punished continue to get punished, and they just accept it after a while. Plus it just sets up a negative relationship with the teacher and school in general.
Positive reinforcement goes a lonnnggg way! Sticker charts, verbal praise, and so on - those things were always useful to me. One idea I got from a colleague was called "magic moments" and it worked like this: When the teacher "caught" a child doing something good, she would hand him a post-it note, upon which he would quickly write what he was doing that helped him earn it. At the end of the day, the children who had received them came up to the front of the class and told the class how they earned it, and got to put a sticker on a chart. There was some sort of reward for earning a certain number of stickers - I used to let kids pick a free book from the monthly book club order as a prize. I used this with second and third graders quite successfully.
With older kids (I also taught sixth grade), a really powerful thing to do is to make a point in the first few weeks of school to call the parents of kids who behave really well and let them know how nicely their child is adapting to their new class. It's especially powerful to call at dinner time - the kids are there, and the parents don't mind the interruption! Believe me, the morning after the first time a teacher does this, all the kids are talking about it, and they all want to be the next one to get a phone call.
I guess this stuff would be helpful to you if you were a teacher looking for ideas, but you're not. Unfortunately, a lot of schools use punishment. I would suggest getting other parents on your side if you want to approach the principal with some new ideas. A teacher who has always used punishment is unlikely to change, though, so you can either think of it as a learning experience for your child and bear with it for the reaminder of the school year, or try to change her class - or at least learn a little about the teachers for the upcoming year and try to request one whose style is more in line with what you would like.