Need some help

My daughter who is almost 14 next month... She is picking and scratching so bad. She is a freshman in high school. School start almost two weeks now. I have been to the school already 2 times this week and once last week. The school is saying that they can not have a child who is in flicking self pain to one self. I don't know what to do... Here is a little information about my daughter: She has been on different meds since she was in first grade for ADHD. We have tried a whole lot of different ones. She has been picking at her face really bad since she was in 4th grade. She would create sores on her hands. Just sit there and pick and pick until she would have a sore. even though nothing was there. I feel that we have her ADHD under control with her meds that we are using currently. In May of this year we were told that she has OCD and that is her picking. Okay no big deal, they have put her on Zoloft. Last school year was really bad, where she would pick her face so bad that the teachers would have to send her to the nurse because of the blood. We started seeing a new dr, who has told us that us telling her to stop picking is like me telling my daughter to stop breathing. This school year she was playing with her dog... And her dog scratched at her arm... He got her good. But they were playing. No big deal. Well since it is trying to heal, she has been scratching at it. However she was scratching pretty hard. She got called up to the office and they are thinking that she is a cutter... NO she is not. I explained to them it was her dog. I explained to them that she OCD, and ADHD. They are telling me that they can't have a child in their school that is creating self in flicked pain to themselves. I have explained to them what the dr has said. But its not good enough for them. Today they told me that this is not normal behavior, but for my daughter this is normal. We must find a way to stop it. I have notice the more you tell my daughter to stop the more it happens. I have found the more you big a deal about it the more she does it. We know she does it when she is stressed out, or nervous. There was a time when I was talking with my daughter, and realized her face was kinda bloody, I asked her if she was picking - her answer no mom... I was not. Then she went and looked in the mirror and saw it. Do this mean she doesn't know when she is doing it? What can I do? Do I continue to fight with the school? Do I continue to seek help if so where do I go? I feel at a lost here. I feel like I have not been a good parent to my child. I don't know what else to do. Please help... Please give me some hope this will stop...