Elementary school students and their parents gather outside their school in New York City on Wednesday to take part in a national walkout to protest gun violence. Students across the United States walked out of classes one month after 17 people were shot and killed at a Florida high school. (Jewel Samadjewel Samad/Agence France-Presse/Getty Images)

This story has been updated.

Tens of thousands of young people across America walked out of school Wednesday to demand action on gun violence, one of the biggest student demonstrations since the Vietnam War protests in the 1970s.

More than 3,000 walkouts were planned across the United States in response to last month’s massacre in Florida, organizers said. Students left class at 10 a.m. local time for 17 minutes — one minute for each victim in the February 14 attack at Marjory Stoneman Douglas High School in Parkland.

Alexia Medero, a 17-year-old at Parkland High School outside Allentown, Pennsylvania, said the issue has too easily gotten lost after past tragedies.

“Families are being torn apart, futures are being stolen, lives are being lost. But we must ensure they are not forgotten,” she said.

Thousands of students gathered on Pennsylvania Avenue in front of the White House, holding colorful signs and cheering in support of gun control. The students chanted: “What do we want? Gun control! When do we want it? Now!”

Students rally in front of the White House on Wednesday. They chanted, “What do we want? Gun control! When do we want it? Now!” (Carolyn Kaster/AP)

At some schools, students didn’t go outside but gathered indoors or wore orange, the color used by the movement against gun violence, or maroon, the school color at Stoneman Douglas.

Some schools applauded students for taking a stand or at least tolerated the walkouts, while others threatened discipline.

The coordinated walkout was organized by Empower, the youth wing of the Women’s March, which brought tens of thousands to Washington last year.

Although the group wanted students to shape protests on their own, it also offered them a list of demands for lawmakers, including a ban on assault weapons and mandatory background checks for all gun sales.

— Associated Press