Talk with your son. It is important to stay calm and supportive. Never yell at your son for bad grades, or threaten him with punishment of any kind. This added stress may only compound his other problems that are contributing to his poor performance in school. Instead, tell him that you are worried about him, and you want him to do well in school so that he will be able to do well in the "real world".
Hire a tutor. Whether you choose a tutoring facility like Sylvan Learning Center, a local college student or an educated adult, a tutor can help your son with one-on-one interaction and support. He can get a customized learning experience that many public schools can't provide due to large class size.
Test your son for learning disabilities. Your local school administrators can put you in touch with a testing facility in your area. Learning disabilities like dyslexia and ADD can cause many students to struggle with coursework, even in subject areas they enjoy. If your child has a learning disability, this may explain any drop in grades. In turn, the school can offer longer deadlines for completing coursework or special distraction-free rooms for testing.
Offer incentives for good grades. These may be monetary incentives, or you may choose to make an agreement where if the child improves his grades, you will buy him something he has been wanting.
Keep an eye on progress reports. Most schools send home progress reports between each quarterly report card. These progress reports can be an early warning of failing grades and can give you time to help your son turn his grades around.
Help him with his homework. Whether it's proofreading his essays, checking his math or helping him build a model, getting involved in your son's daily homework routine can improve his confidence and shows that you care about him.
Cut back on extracurricular activities. Many schools do not allow failing students to play sports or join after-school clubs, in order to allow them to focus on their coursework. You can augment these restrictions with a shorter curfew or by arranging to have your son stay indoors during recess.
Have your child become the teacher. Once a week, have your son teach you one thing he learned in school. This forces your child to not simply regurgitate the information, but to understand it because he has to communicate it effectively to you.
Speak with your child's teachers directly and ask if any extra credit projects or reports can be completed help improve your son's bad grades.