In a parking garage below the Oakland teachers union headquarters on Sunday, dozens of volunteers labored over the banners, posters and picket signs illustrating a historic strike.

A crowd of retired and current educators, college students and district parents with their children turned out for the third “art build” supporting the Oakland Education Association, whose 3,000 members are currently on strike as the union negotiates for higher wages and smaller class sizes.

They spent the Sunday morning cutting canvas, assembling picket-signs and screen-printing images sourced from local artists, including Melanie Cervantes, Favianna Rodriguez and Micah Bazant. The dominant color was red, while the messages, rendered boldly alongside illustrations of women and backpacked children, centered on fighting for the schools teachers and students deserve.

David Solnit, an environmental-justice organizer who’s also married to an educator in Berkeley, brought materials and helped coordinate the event. “About 15 years ago I started reaching out to artists and performers to get involved with actions because, at their core, social movements are really about storytelling,” he said. “And the arts are the most powerful way to tell stories.”

The model, common in activist circles, is gaining traction in public education advocacy. After organizing art builds in the Midwest, Joe Brusky and other workers with the Milwaukee Teachers Education Association got the attention of the National Education Association. Since, they’ve traveled to Los Angeles and Oakland to bring people together over pro-union artwork.

“Generally a union gets 5,000 copies of the sign made at the union printer and everyone’s holding the same one,” said Brusky. “That can be powerful, but it’s not as connected, it’s not as grassroots as collecting multiple images from artists in the surrounding community.”