Give your child extra work to do around the house when she brings home a poor grade. This can take the form of additional chores, such as taking out the trash, doing the dishes or mowing the lawn. Having to put her efforts toward mundane tasks around the house can increase her desire to do school work instead. Just don't overload her with so many household chores that she doesn't have enough time to do her homework.
Take away certain privileges to encourage your child to focus on schoolwork. Your child will miss having access to a computer for fun, a cell phone, television, video games and/or music, providing an incentive to do better in school. If your child needs one of these privileges for schoolwork, such as access to the Internet, stay nearby to supervise how the computer is used.
Punish your child's poor school performance by curbing his social life. For example, ground your child for a weekend or longer, if need be, until he can show that he has improved his grades. Take away your child's Internet access and cell phone, so he can't communicate as easily with friends. Children generally try harder at school when they know that's the pathway to maintaining relationships with friends.
Make a dent in your child's spending power. If she gets an allowance, decrease it or suspend it until her grades improve. If your teenager has a job, she must tell her boss to schedule her for fewer hours in order to dedicate more time to schoolwork. If her grades improve, you can consider whether to allow her to work a few more hours. A positive alternative would be to offer an academic incentives deal to your child: a $5 allowance boost for every A on the next report card.