I had so many thoughts when I read this request. I hope this isn't too long but I think I have good thoughts for you.
1. First of all, how experienced is this teacher? Is she a veteran teacher that has experience? Is she a newer teacher that may not have enough experience is dealing with a classroom of kids effected by holidays and all that stuff that goes on with them at this time of year? Is this a new problem that may be related to the Holidays? If so, then she will settle back down after her routine is back to normal. I know all the kids in my family have gone entirely nuts this month. It is the holidays (Santa's coming) and the knowledge of Christmas break.
2. ADHD is a biological illness that can be effected by many factors such as diet, medicine, environment, and stress. If your child truly has ADD/ADHD you will have to deal with it. Their brain is just randomly firing and things are bouncing around. Have them tested by a Pediatrician that is knowledgeable about it. Medications are different now and many of them don't have the side effects the older ones did.
Have her vision tested, a physical with blood work, a complete workup if this doesn't settle down after Christmas. Is it possible she may have learning disabilities that are causing the problems?
My friend that lives close to Tulsa has a son who kept getting referrals to get tested, she kept observing him and trying to find what was setting him off. She found he was having reactions to red dye #40. As long as his diet is free of it he is this wonderful, great kid who is calm, pays attention, and doesn't have problems outside of normal kid stuff.
2. How ready is she for a classroom situation? My daughter, who is an adult, started having issues in first grade. I went to her classroom and tried to listen to her teacher go on and on about how my daughter wouldn't pay attention. I pointed out to her that I was having trouble paying attention in that classroom. The teacher had pictures on every available wall surface, there were things dangling from the ceiling, there was music playing on a stereo, there was so much going on around me that I just couldn't focus. How was a 6 yr. old going to deal with that? She recommended that my daughter go into transitional first grade. I went ahead and let them, this was the only first grade classroom at this school and I didn't think my daughter would be happy in this classroom with this teacher. We moved to from OKC to Stillwater the next Summer she was more than ready for first grade.
Whether you agree with Freud, Erikson, or Piaget...they all pretty much agree that around age 6 kids should go into the next stage of development where they settle down and begin learning. It is like their little brain has turned on.
3. Absolutely go to school and observe what is going on. First, just watch and see how the teacher interacts with the students, how she works the classroom, take your time, this may give you the answers you need if it is a teacher issue.
Is it possible there is a student she is having a problem with. A best friend she talks to all the time instead of working, a child that bullies her, someone pestering her? So many things can effect how we focus.
Next, if you think it more with your daughter, start working with her and see if you can make a difference. Can you get her to focus? Can you get her attention on the task? Etc...if not, talk to your Pediatrician.
The important thing is that she succeed at school, not that she just makes grades but that she feels like she is succeeding.
Good luck, I hope to hear what you found and how you addressed it.