Thom Hartmann has a simple explanation for why some schoolchildren have so much difficulty paying attention: They are hunters in a world of farmers.

In other words, the distractibility, impulsiveness and risk-taking that can make it hard for them to sit comfortably in a classroom are the same characteristics that were once essential for survival in a hunter-gatherer world.

The American educational system struggles to make them conform, Hartmann says.

"Somehow we got the idea that schools are factories," he said, "but all people are not the same."

Hartmann was the keynote speaker and a workshop leader at this weekend's Missouri ADHD (Attention-Deficit/Hyperactivity Disorder) Conference at Southeast Missouri State University.

His theory, explained in his book, "Attention Deficit Disorder: A Different Perception," was considered "wacky" when originally proposed, he acknowledges. But in December, the prestigious Journal of the American Academy of Children's and Adolescent Psychiatry published an article that in less picturesque language ventured toward similar conclusions.

The controversy over what ADD is and how it should be treated continues, but conferences like this help by getting new information out to those who need it, says Paulette Bruch, co-coordinator of the conference.

Just over 200 nurses, physicians, educators, substance abuse and school counselors, psychologists, and parents from across the state attended the conference. Also present were teen-agers who led a workshop about having ADD.

A number of adults whose children are diagnosed with ADD also find out they have it.

Parenting ADD children is stressful, says Bruch, the mother of two teen-age daughters with ADD. "You worry about their future. Everybody wants their kid to be successful. It's a struggle to deal with their failures, and a lot of them have a pattern of failures."

Peggy Pruett, coordinator of the Southeast Missouri chapter of Children and Adults with Attention Deficit Disorder, is the mother of a 21-year-old with ADD. But her son wasn't diagnosed until he was 16.

"We're trying to educate ourselves so we can help our kids," she said.

Hartmann, whose son has ADD, has written six books about the subject. He has a Ph.D. in homeopathic medicine, is licensed to teach neurolinguistic programming and is the former executive director of the New England Salem Children's Village.

The number of men, women and children in the U.S. who have ADD is estimated at between six and 20 million. Hartmann does not play down the problems they face and does not advocate abandoning traditional treatment tools. "Failing in school is much worse than taking medications," he says.

He does not think of ADD as something that can be cured. "ADD is how we are," said Hartmann, who's more hunter than farmer himself.

At a workshop titled "Healing ADD," he provided some tools for helping people with ADD cope with a farmer world. He demonstrated a visualization exercise he said will turn a bad speller into a good one within 10 minutes.

ADD students need to learn skills to adapt to the farmer environment, Hartmann says.

But our schools also need to change, he insists. "The model we have now is not working."

As examples he cited the one million U.S. families now involved in home schooling and the violence occurring in the schools.

He also wants to change the model for dealing with ADD students, who often have been given up for failures. "Children live up to our expectations," he says.