Poolesville High School students Alice Walker, 17, left, and Rani Powell embrace during a school walkout rally against gun violence outside the Capitol on March 14. (Matt McClain/The Washington Post)

Laura Kirk has never known a pre-Columbine world. Born the year after the shooting at the Colorado high school, lockdown drills have been a regular part of her school experience. At 12, after the shooting at Sandy Hook Elementary School in Connecticut, she was struck with fear that not everyone in her class could cram into a closet if a gunman rampaged through her school.

And on Friday — the 19th anniversary of the Columbine assault, which shattered the concept of schools as safe havens — Kirk and other students in the Washington region plan to walk out of their schools and stage a vigil outside the White House to honor the Columbine victims and others killed by gun violence. The students then plan to march to the Capitol for a rally and to deliver letters to lawmakers calling for tougher gun-control measures.

“Before I was learning how to read or write, I was learning how to sit in a dark classroom to make sure a shooter won’t see us,” said Kirk, a junior at West Springfield High School in Fairfax County. “It’s kind of ingrained in who we are as a generation.”

Friday’s walkout here and elsewhere across the country will mark the latest demonstration in a surge of student-led activism after 14 students and three staff members were shot and killed at Marjory Stoneman Douglas High School in Florida more than two months ago.

Some students plan to demonstrate at their schools, while others say they will get permission from their parents to leave school early and converge in the capital by carpool or public transportation. Thousands are expected in front of the White House, according to a permit application filed with the National Park Service by National School Walkout DC, a student group.

As with a 17-minute walkout that unfolded March 14, school districts have tried to strike a balance between giving students space to exercise free speech and not disrupting learning or risking safety.

In Arlington County, students who leave class Friday without written permission from parents will receive an unexcused absence. Fairfax County school officials are encouraging principals to work with students to find opportunities to express their opinions in ways that don’t intrude on instruction, such as before or after school, or during lunch.

For some teenagers, protesting at school isn’t enough.

Megan Black, an 18-year-old at Patriot High School in Prince William County, plans to walk out of her Virginia school with peers who have passes signed by their parents.

“If people across the country are taking action, I want to be a part of that,” she said. “I wouldn’t feel right sitting in school all day while people my age are out protesting and working for a change.”

Montgomery County school officials said they were hearing little about walkout plans for Friday, after the March 14 protest drew about 2,500 students off campus. They said their position remains the same — that they encourage students to express their views but can’t ensure their safety if they are off school grounds. Students who leave campus are marked as unexcused.

But Brenna Levitan, a 17-year-old at Montgomery Blair High School, said she plans on participating in the rally.

For Levitan, who leads a student group advocating for more-stringent gun-control laws, gun violence is personal. She said she tutors children who have fled violence in other countries but fear shootings in their U.S. schools. One of her friends, she said, tried to commit suicide with an illegally obtained gun.

“The issue is a lot more than just school shootings,” she said. “In fighting this, we need to take all aspects of gun violence into account.”

Officials with D.C. Public Schools said they are aware of students planning to participate in the walkout. The school system sent a letter to parents and students expressing support for students’ right to protest, but said that absences would be counted as unexcused.

Other students will have a tougher time walking out. Some schools are administering national standardized tests this week, and administrators said students leaving in the middle of the day could compromise the exam.

At Thurgood Marshall Academy, a charter school in Southeast Washington, students will not be participating in the walkout, according to Richard Pohlman, the school’s executive director. The school was thrust into the spotlight this year when students from Stoneman Douglas visited the campus to meet their D.C. counterparts, many of whom regularly encounter gun violence in their communities. One of the school’s students, Zion Kelly, spoke at the March for Our Lives rally about his twin brother, Zaire, who was killed in a robbery on his walk home from school in September.

“Walking out of testing won’t be an option as it would create a test security violation,” Pohlman wrote in an email. “Given these challenges, we supported students earlier in the year planning walkout activities when they were announced.”

Friday’s planned walkouts were sparked by Lane Murdock, a 16-year-old at Ridgefield High School in Connecticut, who began an online petition calling for the protest in the aftermath of the February shooting in Parkland, Fla. Walkouts are planned at more than 2,000 schools nationally, Murdock said.

While those students prepare for demonstrations, teens who attend the high school at the center of the day are scheduled to have a day out of the classroom. Columbine High does not hold classes on the anniversary of the 1999 shooting, a practice that began the year after the assault, in which two teens killed 13 people before taking their own lives. Students will instead dedicate the day to community service activities such as volunteering in soup kitchens, participating in a park cleanup and reading to preschoolers.

Scott Christy, Columbine’s principal, and Frank DeAngelis, the principal at the time of the shooting, wrote a letter urging students at other high schools in the county to do the same rather than participate in a walkout.

“April has long been a time to respectfully remember our loss, and also support efforts to make our communities a better place,” the letter read. “Please consider planning service projects, an activity that will somehow build up your school . . . as opposed to a walkout.”

Rachel Hill, a Columbine sophomore, said the principals’ letter was written with input from community members. Columbine students have tried to turn the day into something meaningful by committing time for service. Hill said she doesn’t believe Columbine’s viewpoint was taken into account as the national walkout was planned.

“We feel like doing anything on that day is disrespectful for the families of people who died,” she said. “There’s a time for protest, but it’s not that day.”

Sam Craig — a sophomore at nearby Chatfield Senior High School who organized a walkout involving three schools, including Columbine, earlier this year — said students in Jefferson County, Colo., don’t plan to participate in Friday’s demonstration.

Instead, he said, they prefer to use the day for remembrance. A vigil and rally are planned for Thursday night at a park.

“It’s a really raw and emotional day,” Craig said. “It’s a very difficult day for our whole community. . . . We want to respect Columbine.”