The demonstrations were held on the 19th anniversary of the Columbine High School shooting, which left 13 people dead in Littleton, Colorado. At 10 a.m. in each time zone, students left class to observe moments of silence honoring the victims of Columbine and other shootings.
In downtown Los Angeles, some students made their way from a rally at Pershing Square to L.A. Unified School District headquarters. Officers were at the scene to assist with crowd and traffic control as a police helicopter monitored the peaceful march from overhead.
"It's hard to end gun violence because there's so much going around," said Kayla Lee, a student at King Drew Magnet High School of Medicine and Science. "But I feel like, with the students protesting and stuff like that, we're able to raise awareness in order to enact change in our communities."
At Grover Cleveland Charter High School in Reseda, about 300 students walked out for about 30 minutes before returning to class.
"We need to see changes in our government to prevent mass shootings from happening," said student organizer Jacob Zonis. "So we're talking about banning assault weapons, banning bump stocks. Universal background checks. We're talking about 'no fly, no buy' -- to end people who are on federal no-fly lists from being able to purchase firearms.
"Ultimately, what we want are safe schools and a safe nation," Zonis said.
Meanwhile, at Dorsey High School in Baldwin Hills/Crenshaw, students and officials marked the day with on-campus events.
LAUSD Police Chief Steven Zipperman and Rep. Karen Bass visited classrooms where they spoke with students about school violence and other concerns.
"I'm proud of their actions, whether they're walking in or walking out," Bass said. "I thought it was a great, creative idea to have a 'walk-in.' And I'm happy to participate with them."