LAST AUGUST, I WAS WALKING the Brooklyn Heights Promenade with my then three-year-old son, when he paused in front of a plaque showing the Manhattan skyline as it was, with the twin towers intact. Someone had hung an inexpensive wreath around the plaque that caught his attention. What’s this for? he asked. I could have said, I don’t know, but I realized the 10-year anniversary of 9/11 was weeks away. I wanted him to hear something about it from me first, not a classmate or a teacher.

It is in memory of those towers, I said. There was a terrible fire, and they fell down. Were there people in them? he asked. Yes, I said. Did they die? Yes, I said. Why didn’t they send the fire trucks? They did send the fire trucks, but they couldn’t help. The fire was too big. He was quiet for a moment, and I questioned my parental judgment in telling him even this limited account.

Then he said: Superman should have come to help the firemen. Superman could have saved the people. And he kept walking.

Remembering the conversation later, I realized Superman was designed to do just that. Superman always catches the falling man, fights enemies, pushes the toppling building back into place. Comic books are suffused with sadness (what could be more shocking to a child than the Batman origin story?), but children look to superheroes to transcend their own limitations and those of the world around them. In this instance, Superman eased my son’s fear when he learned that even firemen were mortal; Superman became the metaphorical safe place. And Superman saved me, too, from fear that I had traumatized my son.

I had not thought about that day on the promenade in months, until a visit this summer to the Museum of Modern Art’s exhibit Century of the Child: Growing By Design, 1900 – 2000 (through November 5, 2012) brought it back. The exhibition and its catalog, organized and edited by MoMA curator Juliet Kinchin and curatorial assistant Aidan O’Connor, use design for children as a jumping-off point for a discussion of many of modernism’s larger themes: education, health, consumerism, war, and the role of women in the work place. The exhibition and catalog both follow a rough chronology from the beginning of the twentieth century, when progressive circles focused on the education, dress and health of children as means of developing modern men and women, to the present day, when such concerns recur in design for the developing world. (The “crisis” for first world children, as the catalog notes, now comes from too much food, medication and, especially electronic, toys.)

Despite the utopian bent of the exhibition’s opening galleries, where building blocks and linen smocks rule, as one moves through Century of the Child, there is a certain melancholic undertow. Toys, schools, books, films, and playgrounds reveal themselves in turn as vehicles of adult propaganda or coping mechanisms to paper over trauma. The show makes clear that design responds to needs, but it also fills different kinds of voids. Many of the artifacts on display seem to have been designed as much to save adults from the workaday, violent, consumerist realities of the twentieth century as they were for child’s play.

The first glass case you see as you enter ...