Hi Wendy,
Sounds like you have your hands more than full! This might sound like the opposite of what you're asking for, but I'd encourage you to start changes by catching them doing something right. Positive regard for positive behavior goes a longer way than negative reinforcement or taking stuff away for bad behavior. It just makes 'em resentful & resourceful in ways you don't want them to be. ;) because teens have a way of adapting/sneeking in the things they want from friends & other family members... and you'll just continue the power struggle and everyone will stay miserable.
What's worked for me is a behavior modification intervention from the Parent Project(www.parentproject.org), is to have the kids make a "deserted island" list as a little game: "Make a list of all the things you'd want to have on a deserted island." Meanwhile, you will make a list of all the behaviors you want from each of them: "go to & stay in school all day", "bring up Math to a B", "wash the dishes 2x/week", etc and include stuff they are already doing like "have friends", "eat 1 meal a day at home with family".
Then show each other the lists. The girls might have things like a cell phone, beauty products, time w/friends etc on their lists- great! Those are things that can be added and removed from their life based on compliance w/your list & remember that they are already.
I would really suggest only having about 2 or 3 behaviors on your list for each kid, because we have better outcomes when they don't feel like they're beign asked to "do too much". (I can see your eyes rolling- I remember all the chores I had to do too!) Hey, you can always build on it later, if it works.
Good luck to you & your family~
~DLT