Hi, I'd like to help you with your question.
It is a hard thing to deal with when your child loses motivation in school. There are some things you can try.
You can develop a reward system. Take away all of his privileges and things he enjoys. When he completes his work for a week, give him back one of his things. Also you can talk with him about how to make it easier for him to do his work. Would it help to have a special area for homework? Does he need a break after school, say 30 minutes, to blow off steam? Whatever would make the work easier.
Set up a system for good grades too. For example, if he gets an "A" in a course, he can chose a favorite DVD or PC game for a reward. Talk with him for ideas of what would help him. Sit down and write out what the reward system should be then stick to it.
If none of these work, he may need to talk with a therapist. He may be dealing with a bigger issue such as being afraid of success. Graduating high school and picking colleges can seem overwhelming to even the most well adjusted kids and since you mentioned that he almost wants to fail, I suspect he may be feeling overwhelmed and fearful. He may be resisting the idea of leaving home and going on his own out of fear. Whatever he is experiencing, a therapist can help him gain insight and give him new ways to handle how he feels. You can find a therapist by asking his doctor, or if you attend church, your pastor could help. Also, you can search on line at www.findatherapist.com.
I hope this has helped you,