More of the same BS with her!

Friday morning I got a phone call from my daughter's math teacher. She told me that my daughter got into trouble a few days ago in her class and she was sent home with a letter that I was supposed to sign before she returned to school. My daughter told her teacher that I signed it but she forgot it and left it at home. I told the teacher that I had no knowledge of the letter. She said that she was going to give her in-house suspension for the day because she lied to her. I apologized to her for not knowing about her getting into trouble. Needless to say I was extremely pissed off.
Later that afternoon when my daughter got home from school I asked her why did she lie to her teacher about the letter. Of course she had some dumb ass excuse about how she forgot about the letter and she left it in her desk at school. I so politely reminded her how much I absolutely despise when she flat out lies. I then punched her in the mouth. It wasn't that hard. She wasn't bleeding or anything like that. I just wanted her to feel it. I wasn't trying to really really hurt her. Then I sent her into her room. A few minutes later I remembered it was report card day. So I called her back into my room and asked her where was her report card. Of course I got the same response I always get, "I forgot I had it." WTF... I asked her did she have a child, or a mortgage, or a car note or bills that are due? I told her that all she has to concentrate on is school. I'm sick and tired of hearing that excuse "I forgot" Anyway she showed me her report card and needless to say it looked like TRASH! I told her that she just made my Christmas shopping a whole lot easier. I told her a while ago that her Christmas was only going to look as good as her report card. But then again that has always been the rule. So I called her dad and told him he better not buy her another thing. He agreed with me. He was kinda in the neigboorhood so he stopped by and talked to her. Then I told him to just take her with him. She was really pissed off then because she calls herself kinda cutting him off. She hasn't been over his house in about a month. She used to go every weekend, but she called herself being upset with him. But I made her go because I know I would have been going on and on all weekend about her report card. I didn't feel like wasting my breath and I also wanted to save her the aggravation of me making her feel bad all weekend. So I just wanted time to cool off because I am really sick and tired of her. I have been going thru this with her for the last 4 years with her school work. I have made a decision. Since I feel like I have done everything to try to help her there is one more thing that I thought about but I haven't done. I'm going to call the school and find out how to get in touch with the child study team and I'm going to have her tested to see if maybe she has a learning disability. I know it sounds a little extreme, but I need to know if there is something else wrong with her besides her being a social butterfly. Maybe she is not paying attention because she doesn't understand what's going on and she looses interest so she starts acting up in class. Maybe she is embarrassed because she honestly does not understand what's being taught. I neeed some answers and maybe getting her tested will give me a better perspective on what's going on with her.