Out of control pre-teen!!!!!!?

I have a daughter who just turned 12. She is very mouthy, disrespectful, rude to her parent and grandparent. She doesn't backtalk her teachers but is doing very poorly in school because she rather be social than do school work at home and at school. She is also at the point where her clmates have already formed clicks and each click are going back and forth with some kind of petty crap. She has been given a little more freedom to do things without an adult around like hanging out at the mall (parent is at the mall just not walking around with them), being dropped off at ice skating etc.... but when she goes to these places she gets kicked out of stores etc..... As a result of misbehaving I've taken away her cell phone, laptop, ipod, going places etc..... but none of these things are working. I've also tried rewarding her with things like having a sleepover or going someplace for good behavior but she never manages to get that far. Any suggestions on how to get her under control with the exception of hittng/beating them?