Page 182 - The Intentional Parent

If you don't think this will work, you have at least two other options. First, contact your child's teacher, explain the situation, and suggest that the teacher initiate a conference for the three of you to attend. Perhaps your ex-wife will take suggestions if they originate from the teacher. Second, stay on top of your son's test schedule by keeping in close contact with his teacher. You may have to help him prepare for his Thursday tests on Tuesday nights when he is still with you.
PLAYING ONE PARENT AGAINST THE OTHER
I have one child who is eleven years old, and his father and I have been divorced for two years. We don't really communicate that well, and my son has learned to use this to his advantage. Whenever I won't give him something he goes to his father, and vice versa. I am at a loss for what to do.
It is never too late to begin establishing a more positive mode of communication between you and your ex-husband. Your son is developing a style that relies on manipulating the people he loves in order for him to get what he wants. This is not the kind of behavior you would want him to use in any of his relationships with his friends, peers, or potential girlfriends.
Begin a dialogue with your ex-husband by explaining to him that you have been feeling that both of you are being taken advantage of by your son. Express concern that the child is relying on manipulation to get what he wants. The solution to this dilemma is quite straightforward. It involves more communication between you and your ex-spouse, and a willingness to share decision making. Both of you must feel comfortable enough to respond to your child with neither a yes nor a no when he requests something. Instead, reply, "I'll have to put a call in to your mom (or dad) so we can talk about it.”
The Intentional Parent by Peter J. Favaro, Ph.D. 182