Nearly a month after the nationwide March for Our Lives to protest gun violence in the wake of the Parkland, Fla. school shooting, students around the country will take to the streets again for the National School Walkout on Friday.

The mass protest falls on April 20, the 19th anniversary of the Columbine High School shooting, which up until the Parkland shooting in February was the deadliest high school shooting in U.S. history. On Friday, more than 2,100 schools -- at least one in every state -- are expected to participate starting at 10 a.m. in each time zone. More than 250,000 people have signed a petition on Change.org.

The walkout was organized by Lane Murdock, a 16-year-old student in Connecticut who decided to create the movement following the Parkland shooting. “When I found out about the shooting at [Parkland’s Majory Stoneman Douglas], I remember I didn’t have a huge reaction. And because of that, I knew I needed to change myself, and we needed to change this country,” she told CNN. “We should be horrified, and we’re not anymore. It’s American culture.”

Murdock, whose home is 20 miles from Newtown, Conn., where the 2012 Sandy Hook Elementary School shooting took place, said she had initially planned to coordinate a walkout for just her school, but the movement has rapidly expanded.

The National School Walkout’s website has a planning guide for schools interested in participating for the event. The movement says its three goals are to “Hold elected officials accountable, promote solutions to gun violence” and “demystify and engage students in the political system.” In addition to the walkout, students are encouraged to observe a moment of silence before calling the offices of local lawmakers and “flood social media with calls for reform.”

Students from Parkland like David Hogg have been active on social media encouraging students to participate in the walkout. Participants are being asked to wear orange during the event.