They are the children no parent dreams of having, but many are struggling to raise.

As a group they bear various labels: difficult, challenging, hard to handle, defiant, volatile, willful. For nearly a century, experts have advised parents to employ a variety of often contradictory methods to deal with them.

Yet parents who must navigate the minefield of daily life often complain that they haplessly ricochet from one approach to another, with little or no success.

"Every part of everyday life became a huge task that affected our whole family," said one Washington father, who asked not to be identified to protect the privacy of his son, now 11, whom he described as difficult from birth. "It was relentless."

The confusion and angst surrounding how to cope with a child who routinely throws prolonged tantrums long after the "terrible twos," chronically forgets to turn in homework or otherwise refuses to get with the program are shared by parents whose children wouldn't be defined as difficult. ("Difficult" can be an elastic term that reflects the fit between a parent's and a child's temperaments.)

Now two new books by veteran psychologists offer advice for parents culled from decades of clinical practice. Both volumes emphasize behavior modification, an approach the authors say can be useful for parents who are stymied by difficult behavior that occurs habitually or sporadically.

The authors recommend "positive parenting," which basically urges parents to "catch children being good," coupled with a systematic regimen designed to extinguish unwanted behavior by failing to reward it. Behavioral approaches generally involve setting clear limits, consistently and calmly adhering to them, and prompting and rewarding desired behavior. Some satisfied parents liken the methods to those for training a dog.

"Effective Parenting for the Hard-to-Manage Child" by Washington area psychologists Georgia DeGangi and Anne Kendall (2008, Routledge, $24.95) is written in a workbook format and aimed at parents of children 12 and younger who have a variety of emotional problems. Some take medication for attention deficit disorder, depression or anxiety, while others are socially clueless or stubbornly oppositional. Experts agree that although drugs may help suppress some troublesome symptoms, they do not change difficult behaviors, a point made in both books.

Yale psychology professor Alan Kazdin is the author with Carlo Rotella of "The Kazdin Method for Parenting the Defiant Child With No Pills, No Therapy and No Contest of Wills" (2008, Houghton Mifflin, $26I). /I

Kazdin's regimen, demonstrated in an accompanying DVD, is based on nearly two decades as director of the Yale Parenting Center and Child Conduct Clinic, working with children often referred by schools or courts. Kazdin said his techniques reflect the best available scientific evidence about what works — and more important, what does not.

"Most popular parenting books violate the tenets of what we know is effective," Kazdin said. Many, he observed, advocate that parents "understand your child, talk to your child so he won't be angry. It's wonderful to talk to your child, but talking won't change his behavior for a minute," added Kazdin, president of the American Psychological Association.

Both books reflect an emerging consensus in the field of child development.

"Difficult children have always been around," said Michelle Macias, a professor of pediatrics at the Medical University of South Carolina who chairs the American Academy of Pediatrics section on developmental and behavioral pediatrics. These days, she noted, "the variability of child development and behavior is better understood."

"There is quite a range about what parents consider difficult," Macias added, some of it unrealistic. She said she commonly encounters parents who know nothing about basic child development or workable parenting strategies.

"I see very well-meaning parents who negatively reinforce behaviors they don't want," she said, either by reacting harshly or inconsistently to misbehavior or by endlessly trying to reason with a child.

"It's very common for a parent to attend immediately to a child in a tantrum," which reinforces the behavior. Instead, she advises them to make sure a child is safe and then ignore it or walk away.

"I TELL PARENTS ALL THE TIME, 'ACT, DON'T YAK.' "

MANAGING A MELTDOWN

Kazdin could not agree more.

He said he often informs parents, "I don't want you to KNOW anything, I want you to DO things differently." He advocates that parents practice effective ways to praise, how to punish using brief timeouts or withdrawal of privileges, and what not to do. Harsh punishment, he said, especially physical discipline, can immediately suppress misbehavior but its effects don't last, which is why parents often escalate punishments. Parents who hit or nag, he said, lead to "escape and avoidance" by a child and fail to encourage or reinforce good behavior.

So how does Kazdin handle a 5 year old who has explosive 30-minute tantrums during which he trashes a room?

"That's really easy," said Kazdin whose strategy incorporates the ABCs of behaviorism: antecedent, behavior and consequence.

At home during a calm period, tell the child you're going to play a game. "You say, 'I'm going to pretend to say no and you're going to have a tantrum, but you're not going to hit or throw things. If you can do that, we're going to walk over to the refrigerator and put a star up on your chart,' " which can be turned in for a reward, such as a favorite food or TV time.

"You remind the child it's pretend and then do it. If a child complies, you say, 'I can't believe it, you just stood there when I said no and didn't throw things.' Then you say, 'I bet you can't do it again.' And when the child does, you praise and give another star. If the child fails, you say calmly, 'Okay, no star this time because you threw things. We'll try again later.' "

Practice sessions and positive reinforcement repeated over several weeks, Kazdin said, become the foundation for behavioral change.

"I know it sounds counterintuitive," he said.

Many parents, Kazdin noted, dole out praise ham-handedly, either by making it too general to be meaningful ("Good job!") or by "caboosing" ("Why can't you pick up your toys every time?").

To be effective, Kazdin said, praise should be specific, enthusiastic and immediate. That means telling a child who picks up toys, "That's great! I asked you to pick up your toys and put them in the box, and you did."

ONE PARENT'S EXPERIENCE

Kendall and DeGangi recommend a similar strategy. "One of the things we tell parents who are pulled in so many different directions is, 'You don't have to be perfect, you just have to be good enough,' " Kendall said. "That will take you 80 percent of the way."

"One of the things we emphasize in the book is structure," she said. "Some parents are more gifted at this than others." She said she often sees disorganized parents complaining that their child never remembers to turn in his homework.

The D.C. father said his family is reaping the benefits of a behavioral strategy similar to those outlined in DeGangi and Kendall's book. After years of therapy, medication and frustration, the boy's parents launched a behavioral program six months ago to deal with their oppositional sixth-grade son, who has severe attention deficit disorder.

Before that, the boy used to routinely refuse to get out of bed in the morning for school, resistance that extended to brushing his teeth, eating breakfast or other requests, all of which plunged his family into an uproar that often lasted until the boy went to sleep.

"We would try yelling, punishments, taking away his Game Boy or not going on a ski trip — nothing worked," the father said, adding that his son's problems were jeopardizing his marriage.

Since they instituted a token reward system Kendall helped devise, the toxic before-school hour has improved dramatically.

"He is really interested in getting those points" and is allowed to play a computer game before school if he gets out of bed, brushes his teeth and eats breakfast promptly and pleasantly, behavior his father says has become habitual. "It's become incorporated into our morning routine," he said.

"It took a lot of work," the father added. At first the regimen sometimes seemed overwhelming, but "it's been worth it because he is showing us he can do it."

"It's made a big difference in our family and allowed us to realize that each other isn't the enemy. It's a toehold — but we know we have a very long way to go."