By Gina Cherelus

NEW YORK (Reuters) – Students walked out of classrooms across the United States on Wednesday, waving signs and chanting their demands for tighter gun safety laws, joining a movement spearheaded by survivors of the deadly shooting spree at a Florida high school last month.

The #ENOUGH National School Walkout began at 10 a.m. EDT with 17-minute walkouts planned at 10 a.m. local time in western time zones, commemorating the 17 students and staff killed at Marjory Stoneman Douglas High School in Parkland, Florida, on Feb. 14.

Students arrive for class at Columbine High School before participating in a National School Walkout to honor the 17 students and staff members killed at Marjory Stoneman Douglas High School in Parkland, Florida, in Littleton, Colorado, U.S., March 14, 2018. REUTERS/Rick Wilking

Some students got in an early start. At Fiorello H. LaGuardia High School in New York City, crowds of students poured into the streets of Manhattan, many dressed in orange, the color of the gun-control movement.

“Thoughts and prayers are not enough,” read one sign, needling the rote response many lawmakers make after mass shootings.

In Parkland, students slowly filed onto the Stoneman Douglas school football field as law enforcement officers looked on.

The walkouts are part of a burgeoning, grass-roots movement that grew out of the Parkland attack. Some of the survivors have lobbied state and federal lawmakers, and even met with President Donald Trump, to call for new restrictions on gun ownership, a right protected by the Second Amendment of the U.S. Constitution.

“If our elected officials don’t take responsibility for their inaction on both sides of the aisle, then we are going to kick them out of office,” David Hogg, a Stoneman Douglas student, said in an interview with MSNBC on Wednesday.

The students’ efforts helped bring about a tightening of Florida’s gun laws last week, when the minimum age for buying any kind of gun was raised to 21 years from 18, although lawmakers there rejected a ban on the sort of semiautomatic rifle used in the Parkland attack.

In Washington, however, plans to strengthen the background-check system for gun sales, among other measures, appear to be languishing.

A large crowd of students gathered and chanted slogans outside the gates of the White House. Trump, however, was out of town on a trip to California.

Students from more than 2,800 schools and groups are joining the walkouts, many with the backing of their school districts, according to the event’s organizers, who also coordinated the Women’s March protests staged nationwide over the past two years.

Support has also come from the American Civil Liberties Union and Viacom Inc <VIAB.O>, which said all seven of its networks, including MTV, would suspend programming at 10 a.m. in each U.S. time zone during the 17-minute walkout.

The protests took place a day after Florida prosecutors said they would seek the death penalty for Nikolas Cruz, who has been charged with 17 counts of premeditated murder and 17 counts of attempted murder in the Parkland attack.

The New York City Department of Education allowed students to participate if they submitted a signed permission slip from their parents.

But a few school districts around the country had warned against protests during school hours.

Administrators in Sayreville, New Jersey, told students that anyone who walked out of class would face suspension or other punishment, according to myCentralJersey.com.

(Reporting by Gina Cherelus in New York; Additional reporting by Jonathan Allen and Alice Popovici in New York, Joe Skipper in Parkland, Florida, and Susan Heavey in Washington; Editing by Frank McGurty and Jonathan Oatis)