Nearly 3,000 walkouts began at 10 a.m. in the biggest demonstration yet of the student activism that has emerged following the massacre of 17 people at Marjory Stoneman Douglas High School.
Education officials and city leaders across the New York area encouraged students who so desired to walk out of class. In fact, Mayor Bill de Blasio was at Edward R. Murrow High School and expected to make a speech.
The walkouts Wednesday are expected to last for 17 minutes, for the 17 people killed in Parkland on Valentine's Day.
Schools Chancellor Carmen Farina sent a letter to parents saying middle and high school students who wish to walk out, with or without parental permission, won't be disciplined beyond noting on their record that they cut class. But other districts aren't planning to be so accommodating.
At Sayreville War Memorial High School in New Jersey, students were told they'd get suspended if they walked out, and that's a tougher penalty than normal.
"The students are kind of mad at it," one student said. "Why such a drastic change in policy because of the political protest for us?"
In other parts of the country, students from the elementary to college level are taking up the call in a variety of ways. Some planned roadside rallies to honor shooting victims and protest violence. Others were to hold demonstrations in school gyms or on football fields. In Massachusetts and Ohio, students said they'll head to the statehouse to lobby for new gun regulations.
The coordinated walkout was organized by Empower, the youth wing of the Women's March, which brought thousands to Washington, D.C., 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 group said on its website.
It's one of several protests planned for coming weeks. The March for Our Lives rally for school safety is expected to draw hundreds of thousands to the nation's capital on March 24, its organizers said. And another round of school walkouts is planned for April 20, the 19th anniversary of the Columbine High School shooting in Colorado.
After the walkout Wednesday, some students in Massachusetts say they plan to rally outside the Springfield headquarters of the gun maker Smith & Wesson. Students and religious leaders are expected to speak at the rally and call on the gun maker to help curb gun violence.
At Case Elementary School in Akron, Ohio, a group of fifth-graders have organized 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 will line a sidewalk along a nearby road, carrying posters with the names of Parkland victims.
The walkouts have drawn support from companies including media conglomerate Viacom, which said it will pause programming on MTV, BET and all its other networks for 17 minutes during the walkouts, and students will temporarily take over MTV's social media accounts.
In suburban Atlanta, one of Georgia's largest school systems announced that students who participate 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," Kleinman said.
Other schools sought a middle ground, offering "teach-ins" or group discussions on gun violence. Some worked with students to arrange protests in safe locations on campus. Officials at Boston Public Schools said they arranged a day of observance Wednesday with a variety of activities "to provide healthy and safe opportunities for students to express their views, feelings and concerns." Students who don't want to participate could bring a note from a parent to opt out.
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 will provide free legal help to students who are punished.