Schoolchildren across the US plan to walk out of school on Friday to demonstrate against gun violence.
The National School Walkout marks the 19th anniversary of the Columbine High School massacre in Colorado.
Connecticut high school pupil Lane Murdock set up the event in the wake of the Parkland shooting in Florida.
Students will leave school at 10:00 across America’s time zones. Schoolchildren in every state are expected to participate.
The goal of the demonstration, which involves more than 2,000 schools, is to raise awareness of gun violence and to combat political inaction.
Ms Murdock launched the National School Walkout campaign in the wake of the Parkland shooting in Florida.
The protest started as a petition on the website change.org. More than 250,000 people have signed it.
“I’m from Connecticut where Sandy Hook happened – I’ve been surrounded by this reality all of my life,” she told the BBC.
Participants on Friday will leave school and gather for 13 seconds of silence, in honour of the 13 victims of the Columbine shooting.
The sample walkout agenda from the campaign says the students will not go back to school but instead will “make calls to their Senators’ offices and flood social media with calls for reform”.
US students already staged a national walkout on 14 March, one month after 17 people were murdered at Marjory Stoneman Douglas High School in Florida.
What was the Columbine massacre?
- Eric Harris and Dylan Klebold murdered 12 students and one teacher on 20 April 1999, before killing themselves
- 24 more people were injured in the attack, mostly by gunfire
- As well as guns, the pair used nearly 100 explosive devices, including a bomb placed in the school’s cafeteria that didn’t detonate
- The shooting caused a national outcry, leading to changes in police tactics and investigations into violent video games and bullying
Major celebrities have also got involved in the walkout.
Actors Robert DeNiro and Julianne Moore penned absence letters for students to explain why they were participating.
Students who survived the Florida shooting have actively advocated for an end to gun violence, with many backing legislative changes to control the sale of guns.