Warning that their futures are being stolen from them, tens of thousands of young people across the U.S. walked out of school to demand action on gun violence today in one of the biggest student protests since the Vietnam era.

Braving snow in New England and threats of school discipline in places like Georgia and Ohio, they carried signs, chanted slogans against the National Rifle Association and bowed their heads in memory of the 17 dead in the Feb. 14 shooting at Marjory Stoneman Douglas High School in Parkland, Florida.

“We’re sick of it,” said Maxwell Nardi, a senior at Douglas S. Freeman High School in Henrico, Virginia, just outside Richmond. “We’re going to keep fighting, and we’re not going to stop until Congress finally makes resolute changes.”

Across the country and beyond, students were urged to leave class at 10 a.m. local time for 17 minutes — one minute for each of the dead in Florida. At some schools, students didn’t go outside but lined the hallways, gathered in gyms and auditoriums or wore orange, the color used by the movement against gun violence, or maroon, the school color at Stoneman Douglas.

Over and over, students declared that enough is enough, that too many young people have died, and that they are tired of going to school afraid of getting shot.

“I don’t want my mother or my father having to worry about me going to school getting an education and then my life is gone,” said Leticia Carroll, a 15-year-old freshman who helped organize a walkout of more than 100 students at Groves High School in Beverly Hills, Michigan, outside Detroit.

She added: “We need answers. We need something done.”

Alexia Medero, a 17-year-old at Parkland High School outside Allentown, Pennsylvania, said the issue has too easily fallen by the wayside 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.

In joining the protests, the students followed the example set by many of the survivors of the Florida shooting, who have become gun-control activists, leading rallies, lobbying legislators and giving TV interviews. Their efforts helped spur passage last week of a Florida law curbing access to assault rifles by young people.

In Washington, more than 2,000 high-school age protesters observed the 17 minutes of silence by sitting on the ground with their backs turned to the White House as a church bell tolled. President Donald Trump was in Los Angeles at the time.

The protesters carried signs with messages such as “Our Blood/Your Hands” and “Never Again” and chanted slogans against the NRA.

In New York City, they chanted, “Enough is enough!”

Stoneman Douglas High senior David Hogg, who has emerged as one of the leading student activists, livestreamed the walkout at the tragedy-stricken school on his YouTube channel.

He said the students could not be expected to remain in class when there was work to do to prevent gun violence.

“Every one of these individuals could have died that day. I could have died that day,” he said.

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

About 10 students left Ohio’s West Liberty-Salem High School — which witnessed a shooting last year — despite a warning they could face detention or more serious discipline.

Police in the Atlanta suburb of Marietta patrolled Kell High, where students were threatened with unspecified consequences if they participated. Three students walked out anyway.

The coordinated protests were organized by Empower, the youth wing of the Women’s March, which brought thousands to Washington last year. It offered the students a list of demands for lawmakers, including a ban on assault weapons and mandatory background checks for all gun sales.

Congress has shown little inclination to tighten gun laws despite the recent mass shootings, and Trump backed away from his initial support for raising the minimum age for buying an assault rifle to 21.

Education Secretary Betsy DeVos had no immediate public comment on the walkout.

Historians said the demonstrations were shaping up to be one of the largest youth protests in decades.

“It seems like it’s going to be the biggest youth-oriented and youth-organized protest movements going back decades, to the early ’70s at least,” said David Farber a history professor at the University of Kansas who has studied social change movements.

“Young people are that social media generation, and it’s easy to mobilize them in a way that it probably hadn’t been even 10 years ago.”

The walkouts drew support from companies including media conglomerate Viacom, which paused programming on MTV, BET and all its other networks for 17 minutes during the walkouts.

Other protests planned in coming weeks include the March for Our Lives rally, which organizers say is expected to draw hundreds of thousands to the nation’s capital on March 24.