Every Christmas, the boy put in requests to his father for toys that made noise, went fast and roused parental cringes. The father -- a writer, a man of reflection and content to live in the slow lane -- shudders when telling about the call one year for the zenithal in sound and speed, a Honda motorcycle.

This Christmas is different. The son, now 18 and a junior in high school, has asked for a typewriter, a tool of the mind.

He'll get it. For the father, the typewriter symbolizes the gifts of love, patience and confidence that he has been offering his son all along. The boy has what is called "the hidden handicap," a learning disability. His wanting a typewriter, to be used for school assignments, is being taken by his father as a message: thanks for keeping faith in me.

This Christmas story is best understood by the families of other learning- disabled citizens. But with researchers and teachers continuing to broaden the field of study that began only 15 years ago, the handicap still needs to be better understood by more than the specialists. The learning disabled -- in numbers ranging from 3 million children to a possible 10 million -- live among all of us, and our obligation is not to be self-disabled in learning about them.

Few are better teachers, both in her classroom and in the national forum, than Prof. Sally Smith, who runs the learning disabilities program at American University and who founded and directs the Lab School in Washington. Smith, who believes that uncounted millions of adults are also learning disabled, says that at least a few children in every classroom have the handicap. In every classroom, too, it is likely that a few well-meaning theories on "curing" the handicap are floating about.

In "No Easy Answers: The Learning Disabled Child at Home and at School" (Bantam Books), Smith writes that sudden cures shouldn't be sought. Instead, "each teacher must be a detective of sorts to determine how each child learns best, what modalities or channels of learning are a child's strongest ones, what interests can be built on, what specific disabilities are there to remediate."

In reading Smith's gripping book, and spending time with her the other afternoon, I came to feel that she is the Maria Montessori of our day. Her idea of matching the method to the child is like Montessori's call for a school to be "a pleasant environment where the children felt no restraint." Also like Montessori, Smith has been successful in her theories of education. In 16 years of teaching several thousand children, all but one have graduated from high school and most have gone on to college.

The learning disabled, whose symptoms include lack of concentration, poor speech, reading problems, clumsiness, immaturity and left-right confusion, have a history of going on to higher things. Their ranks have included Einstein, Nelson Rockefeller, George Patton, Amy Lowell and Yeats. But none has succeeded without wise teachers or without parents -- though pained by seeing their children pained -- who refuse to become defeatists.

At a gathering last week of friends of the Lab School, one of those parents, Ann Bradford Mathias, rose to share the fact that she herself, in her mid-50s, is learning disabled. "I was one of those classroom statistics, one of those intelligent children who could not learn -- or as I prefer to put it, one of those intelligent children who learned differently. A heavy dash of New England contrariness and a little bit of luck and a lot of patience on the part of others are the ingredients I suspect that enabled me to survive in a world that then, as now, measured success by how well one did in school. . . . I did graduate from school, eventually, though it took longer than considered normal. I did astound my parents and every teacher who had known me when I was finally accepted by one of the Seven Sisters (Vassar College) as a risk. . . . But this success was not without its tribulations. And it is because of this tribulation that I say I wish there had been a Lab School in my life, for I would have been helped to discover sooner the giddy excitement of academic accomplishment."

Ann Mathias, chairman and president of the board of trustees at the Lab School, is married to Maryland's senior U.S. senator. She rarely speaks this personally in public about her learning disability. That she did now is a generous Christmas gift we can all share.