She leans back in her rocking chair and says, "I always tell people there are three child-raising theories worth knowing about: Montessori, Piaget and the Mitchell-ian."

Grace Mitchell, 72, author of three books on the subject and founder of a national day-care center, leans forward to explain:

"It revolves around four simple words: I am, I can. If you teach a person to feel good about themself there isn't anything they can't do -- parent, teacher or child."

Mitchell, the mother of criminal defense attorney F. Lee Bailey, was in Northern Virginia to conduct a workshop on classroom discipline. Despite the changing attitudes on the subject, she says it is the one area about which parents and teachers have sought advice persistently throughout her almost half a century of child-care work. Although there is no one set of directives, Mitchell counsels adults to employ the same philosophy they would use in trying to teach a child anything.

"A child needs to see the sense of acting in a certain way . . . to learn self-discipline," she says.

This can be taught, Mitchell says, by explaining why certain behavior is desirable and establishing the ground rules for punishment before any infraction occurs. Above all, she urges parents and teachers to use common sense in disciplining children -- don't "paint yourself into a corner" by threatening something that cannot be carried out, and remember that despite spurts of cantankerous behavior, children primarily want to please.

"Use your trump card -- don't ever forget that your child loves you and wants more than anything else to please you . . . don't concentrate so much on what the child has done, but on why they may have done it," she advises.

On physical punishment -- always a controversial subject -- Mitchell urges the parent to be cautious about spanking and to consider what it may accomplish or teach the child.

"I won't say that it is always wicked to spank a child's bottom, but usually, spanking is more a relief for the parent than anything else," she observed. "I always remember the story of the woman on the train with two children, a 2-year-old and a 4-year-old. The 4-year-old struck the 2-year-old and the mother, incensed, turned to the child, hit him, and said, 'I'll teach you to hit people' -- and she did."

Although she is considered the grande dame of child care by many, Mitchell's began her child-care career with the same step taken by most parents. She had a child, Bailey. It was during the Depression and her husband was out of work, so when her sister suggested that the former schoolteacher run a nursery -- a term then unknown to Mitchell -- she decided to give it a try.

"I was very poor, very pregnant and very bored . . . and I didn't even know what a nursery was," the ashen-haired woman recalls, adding, "But neither did most of the people whose doorbells I rang."

Some 30 children -- a few paying a dollar a week, most less -- responded, and gathered in her five-room apartment. And there, in Waltham, Mass., 47 years ago, were the sketchy beginnings of a child-care dynasty that eventually grew to include 47 day-care centers -- Living and Learning Centers Inc., a nursery, a doctorate in education, three books and now, her most recent interest, a consulting firm for corporations interested in developing day-care centers.

"Its the hottest item," Mitchell declares, referring to her newest partnership. "Ten years ago, industry turned off its hearing aid to day care. Today, they're calling us. The day is coming fast where we will see a day-care center in the middle of every office complex."

Mitchell attributes the surge of interest among employers to a realization that day care makes sense financially, not to any sudden burst of altruism. With child care facilities on the premises, absenteeism declines, so worker's productivity increases.

She says companies have also discovered that if they offer day-care services to employes, the cost of training and hiring replacements for pregnant women drops because new mothers return to the work force much sooner and the need for a large temporary work force decreases.

"It's far more than a social responsibility. It helps the bottom line," she explains.

Unlike many in the social programs field, Mitchell does not fear the knife of President-elect Ronald Reagan. Day care, she insists, is here to stay. Parents may have to pay more for services if some federal funds are cut, but with more than half of American women working, and with single parents comprising a large part of the labor force, Mitchell insists that anyone with a financial vein in his body -- the very stuff of which Republicans reputedly are made -- would be foolish to make it more difficult for people to work outside the home.

"Day care will have to survive," she insists. "It is no longer a matter of should we have it -- we have to have it. Common sense dictates most people can no longer feed their families with only one income."

To parents flustered and bewildered by what sometimes appears an unending clash between a child's will and a parent's wishes, Mitchell points out that life with Bailey and her two other children was not always harmonious for her, either. She acknowledges that she made mistakes, spanked when she should not have, and often was unable to understand the workings of Bailey's mind.

"He was never my baby. He always had the mind of an old man," she says, her blue eyes sparkling. "Even when he was 6 months old, I knew he was different. He was always way ahead of me and, once he made up his mind, he was immovable.

"Living with Lee was like living on the edge of a 10-story building."

There are many things, she says, that she would approach differently were she a mother today and knew what she knows now. But, like most mothers -- including all the ones who don't hold doctorates in education, have not cared for thousands of children or written books on the subject -- when she is asked how she would have preferred her children to develop, she pauses, then pours forth an avalanche of praise:

"He's generous, he's kind; she's successful, they're wonderful. . . ."

Quietly, she begins to rock again.