I have this same problem with my 14 year old daughter. She has become very mouthy with her step-dad and myself. So we have recently decided to put her on "lockdown". This may sound harsh, but really all it is, is a total grounding from EVERYTHING she loves. She is not allowed to watch TV, no iPod, no talking on the phone, no leaving the house and most importantly NO COMPUTER. That last one really gets her where it hurts. My husband and I have decided it will be this way until she can start showing respect. When she starts doing this, we will slowly give her back limited use of her privledges. I know this doesn't always work with all kids, but so far she has shown a little improvement.