Be specifically prepared for the child's avoidance, distractions, and excuses
You know your child's typical moves. Make a list of these. When your child displays one of these, calmly show him the list and ask his help in checking off which excuse or avoidance this one is. Reward him for cooperating with the checkoff process. (The helps to establish a working cooperation, even if it begins by agreeing about excuses.)
Do not argue with your child. Be calm (you should work on this ahead of time), and remind him of the rules, agreements, and consequences.
Using a baseline of his avoidance or distractions, reward him for doing less of this each time. (For example, if your child gets distracted or gets up from his work five times during a homework session, reward him for lowering that to four, etc.)
Focus your child on sitting down on time at a designated place and staying there for the specified homework time (planned ahead by agreement). Do not attend to complaints, whining, etc.
Remind him of the basic agreement you made with him about homework (again this takes some planning and advanced legwork) and hold him accountable by consequences.
Turn frustrating encounters into successful outcomes
Define small successes along the battlefront. If your child hates sitting down to homework, try rewarding just showing up at the table with materials. That could be a major start for a few days.
Challenge your child to make an agreement with you that homework will produce no yelling or tears, regardless of the work that gets done. This is a basis for emotional bonding, support, and cooperation.
Figure out how long your child can go before becoming frustrated or avoiding (this may be only a few minutes at first) and reward him for time-on-task before that point. For example, if your child has a 50% probability of sustaining attention for 10 minutes, but has an 80% probability of sustaining attention for 3 minutes, plan the initial reward at 2 minutes. Thus, you build upon and extend his entering behavior.
Bargain with your child to increase the value of your help. For example, if your child can't solve a problem and needs your help, or if he complains, "That's not the way the teacher showed us," make a deal with him that exchanges your help for his respect and follow-through. Try the "You scratch my back and I'll scratch yours" approach on a very small scale when your child itches for your help.
Know the homework before your child starts
One common frustration is that parents don't know what the homework actually is. So, when the child says, "I finished it," or "We didn't have any today," or I left it at school," you can be prepared by having a copy of the homework.
Have a copy of your child's homework daily in advance of homework time. Ask the teacher or school secretary to FAX you the homework before your child gets home. (e-mail sometimes works, but it won't look like what your child copies from the board.) The idea is to have an exact replica of what your child should have.
Get a time estimate from the teacher of how long this homework should take, when it is due, and how it is to be collected or turned in.
If necessary, have extra copies of the books and materials at home in case your child "forgets."
Teach consequences, not subject matter
Unless you are homeschooling, your job is not to teach subject matter. Your job is to monitor and supervise your child's increasing skills, habits, and independence regarding assigned work. Give your child a helpful hint, a word of encouragement, and then walk away.
Have a clear plan of consequences for all potential homework outcomes. For example, "If all your work is completed on time, you get this. If the work is not done, you don't get this. For each time I help you, it costs you this."
Recognize that (incredibly) the difficult child gains substantial reward by observing your frustration. Also, reminders and nagging quickly become cues to signal when you really mean it (e.g. you really have to to it the fifth time I raise my voice). Cut out these unproductive reinforcers.
Allow consequences the time and cumulative power to exert their effects. Your child needs to learn consequences through his experience, not through words and threats.
Guest information: Dr. Mark Steinberg has worked with children, adolescents, and adults for over 33 years. He is a licensed Psychologist and Educational Psychologist who remediates and heals attentional, behavioral, emotional, and learning difficulties. For more information on this topic or to contact Dr. Mark Steinberg: http://www.marksteinberg.com/.