Young people in the U.S. walked out of class to demand action on gun violence Wednesday in what activists hoped would be the biggest demonstration of student activism yet in response to last month’s massacre in Florida.

More than 3,000 walkouts were planned across the U.S. and around the world, organizers said. Students were urged to leave class at 10 a.m. local time for 17 minutes — one minute for each victim in the Feb. 14 attack at Marjory Stoneman Douglas High School.

Students from elementary school to college planned to take up the call in a variety of ways. Some were expected to hold roadside rallies to honor shooting victims and protest violence. Others planned demonstrations in school gyms or on football fields. In Massachusetts and Ohio, students said they would head to the statehouse to lobby for new gun laws.

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 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.

“Our elected officials must do more than tweet thoughts and prayers in response to this violence,” the organization said on its website.

Other protests planned in coming weeks include the March for Our Lives rally for school safety, which organizers say is expected to draw hundreds of thousands to the nation’s capital on March 24. Another round of school walkouts is planned for April 20, the 19th anniversary of the Columbine High shooting in Colorado.

Some students in Massachusetts said that after Wednesday’s protest, they planned to rally outside the Springfield headquarters of the gun maker Smith & Wesson.

At Case Elementary School in Akron, Ohio, a group of fifth-graders were organizing a walkout with the help of teachers after seeing parallels in a video they watched about youth marches for civil rights in 1963. Case instructors said 150 or more students were expected to line the sidewalk, carrying posters with the names of Parkland victims.

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

Districts in Sayreville, New Jersey, and Maryland’s Harford County drew criticism this week when they said students could face punishment for leaving class.

In suburban Atlanta, one of Georgia’s largest school systems announced that students who participated might face unspecified consequences.

But some vowed to walk out anyway.

“Change never happens without backlash,” said Kara Litwin, a senior at Pope High School in the Cobb County School District.

The possibility of being suspended “is overwhelming, and I understand that it’s scary for a lot of students,” said Lian Kleinman, a junior at Pope High. “For me personally, this is something I believe in. This is something I will go to the ends of the Earth for.”

Other schools sought a middle ground, offering “teach-ins” or group discussions on gun violence.

Meanwhile, free speech advocates geared up for a battle. The American Civil Liberties Union issued advice for students who walk out, saying schools can’t legally punish them more harshly because of the political nature of their message. In Pennsylvania, Wisconsin and Texas, some lawyers said they would provide free legal help to students who are punished.

Associated Press writers Jeff Martin in Atlanta and Kantele Franko in Columbus, Ohio, contributed to this report.