It’s the perfect place for chalk art—the rain and the wind almost always approach the museum from behind so that drawings remain sheltered by the eaves, staying on the walls for weeks at a time.

Of course, it might all go to waste if John Aaron, the director of the Museum of Modern Arf and this year’s Modern Arf’s My Neighborhood Chalkfest, weren’t standing watch. “I was up ’til 3 last night, guarding the walls,” he says, pointing at the chalk-festooned edifice and explaining how the gallery’s location, in an alley just off Wilson Boulevard in Clarendon, makes it a prime location for revelers looking to relieve themselves. Aaron has no compunction about running them off.

There aren’t a lot of things that give Aaron pause. He boldly claims that Modern Arf is “the only art gallery in the world where you can bring your dog inside,” and the artist is best-known for his offbeat depictions of pets. But at Oct. 15’s Clarendon Day, the neighborhood’s annual celebration of local merchants and artists, Aaron is all about the chalk.

Aaron has hosted at least five similarly sized “chalk-ins,” plus a number of “chalk parties” not aimed at children. This year’s My Neighborhood Chalkfest is meant to raise awareness for Aaron’s plan to launch Chalk4Peace, a worldwide event to be held next fall, for which the artist hopes to get a million children around the world to draw in the name of peace.

His own childlike spirit—as he walks to the gallery with a bunch of helium balloons, he stops folks on the street and jokes, “I asked my boss for a raise and he said, ‘Just hold on to a bunch of these!’”—led Aaron, a lifelong political activist, to discover chalk-ins as a tool for building awareness. It may not be the most sophisticated medium, but Aaron says that its association with children—who often have raw, emotional responses to war and injustice—is part of its charm.

“Children are the greatest artists, especially between, say, 8 and 12, when they’ve got the motor skills to draw but haven’t had the purity of their response bred out of them,” he says, “or gone off and become interested in being cool.”

On the morning of Clarendon Day, the crowd skews a bit younger than that of most of Aaron’s previous chalk-ins, leaning toward families with younger children.

The festivities are free (though Aaron does solicit donations), but “I always have to tell parents, ‘I’m not a baby-sitting service,’” says Aaron. “‘If you dump you kid here for two hours, you owe me 50 bucks.’”

While the kids dive into the buckets of chalk and pastels that Aaron has provided, the parents stand around as Aaron tells them his dream of children drawing for peace. The parents seem receptive; many are happy to chat about politics.

But the kids don’t talk about war. And they certainly don’t try to draw it. They draw their families, their favorite animals, jack-o’-lanterns. One kid just writes, “Darby Rules!” over and over again. It’s not a movement—it’s chalk.

Which raises the question: What do children know about war and peace?

Aaron draws a large peace sign on the street and encourages children to color it in. Miranda, age 4, grabs her friend Rebecca, also 4, by the hand and brings her over to the side of the road to see what Aaron is doing.

“What’s that?” asks Rebecca, pointing at the oddly divided circle.

“It’s a pizza!” Miranda cries, and the two laugh and color in the sections with a mixture of pink, white, and orange.

When they’re done, Miranda announces that she likes this new shape. She draws another one all by herself and colors this one red, white, and blue. —Jesse Stanchak