Taking things way ex: tv, games, computer, going outside to play. Those normally work the best because when you take those things away all they have left to do is school work and chores which will soon boost there grades back up. Once they start improving then you can slowly give them something back as a reward.
I don't need to have sex, my government fcks me everyday.
Be careful of the toes you step on today
They just might be connected to the ass you kiss tomorrow.