he walls of the first-grade classroom held the same timeless decor: February written in block letters. A valentine. A picture of Abraham Lincoln's log cabin. An announcement about George Washington's place in American history.

But seated in a semicircle on the floor of the room, a class of small children spent an hour with the cameras and sound equipment talking about what one child called "the nuclear." They were being filmed for a medical research program to show us what, and when, children know about nuclear weapons in the world.

The contrast between the history on the walls and the contemporary terror on the floor was not as striking to me as it might have been. This was, by the oddest of coincidences, the building where I had gone to grammar school.

Down one of these traditional, beige hallways, my own generation of school children, the first nuclear-age children, had filed to basement air raid shelters at the sound of the alarm. We had been the subjects of the civil defense of the '50s, a defense whose naivet,e filled the uproarious documentary film, "Nuclear Follies," with endless film clips of schoolchildren ducking the A-bomb under their desks.

That was how our elders had tried to reassure us; this was how our elders pretended, for themselves and for us, that they could still protect us.

Listening to the first-graders who were just beginning to understand "the nuclear," listening earlier to videotapes of third-, fifth-, seventh-grade and high school students as they tried to cope with fear and denial, with hopelessness and a diminished belief in the future, I tried to imagine what kind of reassurance today's adults can offer.

What can we say without becoming part of some civil defense farce, without lying? How can we, who also experience fear and powerlessness, give children a belief in the future?

Roberta Snow, who has interviewed at this school and many Massachusetts schools this past year as chief investigator of the project, has asked herself that question. "As an adult, it's very difficult not being able to comfort your children. You want to look them in the face and say, 'You'll never starve, there'll never be a war, I'll always be here.' But we can't honestly do that."

Still, Snow has found some levels at which parents, teachers, adults, can in fact be reassuring. The younger children she has met have some fantasies that are even worse than the reality.

One third-grader has heard about "the button" so much that she envisioned buttons everywhere that anyone could push. Another child thought that nuclear bombs were small enough to be carried around by anyone, like Saturday-night specials. A third believed that one bomb alone could destroy the world.

If these children were actually relieved by the facts, others felt better when they discovered that the grown-ups also knew about the threat of nuclear war. "Many kids," said Snow, "were reassured just to discover that adults know what's going on, know that kids are scared and let them be scared without saying, 'Don't be ridiculous.'

"The most important thing wasn't what adults said, but how they listened."

As for the older children, it was hardest to deal with those who, just like my teen- age generation, blame their elders for this nuclear mess. They are, as Snow said, "trying to make sense of a world that has the capacity to blow up so fast, and angry that they may be robbed of their future."

Teen-agers in particular believe what they see of our lives more than what we say to them. The only genuine comfort that one nuclear generation can offer the next is our activism, in the sense that we're working in our own ways to reduce risks.

This pushes us to break through layers of denial: our own unwillingness as adults to confront the reality of this threat. Our unwillingness to admit that young children, our children, know about this nuclear threat and that their lives are profoundly affected by it.

The only ultimate protection is prevention. But our children, living with this monster, deserve to be heard, deserve to understand that we know about their fears, share their fears, and are working to make this a less scary world.

My parents' generation tried to comfort themselves and us with air raid drills. In this school, the elders taught my classmates to duck the bomb. Now, in the same buildings, children are asking us to stand up again.

c1983, The Boston Globe Newspaper Company