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They chanted, carried signs, made a human peace sign in the rain and even broke through school gates in a sign of defiance, joining tens of thousands of other students who walked out of classes Wednesday throughout the Bay Area and across the nation to protest gun violence.

In one of the largest student demonstrations since the Vietnam War, the nationwide school walkout began in a wave across time zones at 10 a.m. and lasted 17 minutes — one for each of the victims of the Parkland, Florida, high school shooting exactly a month earlier.

“I think anybody has the chance to get gun laws changed,” said sophomore Stephanie Redding, 16, who was among some 200 Heritage High School students in Brentwood who walked out. Her district has seen several threats of violence in recent weeks, and students organized a “Walk Up” where they wrote reasons to positively change the school climate on a chalkboard.

While most of the Bay Area walkouts were peaceful, Concord’s Mt. Diablo High School became a flash point when students burst through a locked gate to march off campus, and a San Leandro school was briefly locked down after a threat.

At about 10 a.m., Mt. Diablo High made an announcement over the loudspeaker to honor the victims of gun violence. Principal Lorne Barbosa said he was not opposed to students participating in protests but that the student government had decided not to do a walkout. So the school locked its gates thinking parents wouldn’t want students leaving campus.

But students marched out of class anyway and broke through a back gate to continue down Grant Street, shouting “enough is enough.” The students walked back when administrators said they would make calls to parents, and school staff re-locked the broken gate.

Lila Souza, a sophomore at Mt. Diablo who had organized students to participate in the nationwide protest, said she did not expect the gates to be locked or that students would break through — nor did she want what was supposed to be a peaceful march to become destructive.

Women’s March Youth Empower, a politically liberal group of high school and college students from around the country, organized the march “to protest Congress’ inaction to do more than tweet thoughts and prayers in response to the gun violence plaguing our schools and neighborhoods.”

The march highlights the growing student unrest over gun violence ever since authorities say Nikolas Cruz, 19, strode into Marjory Stoneman Douglas High School in Parkland on Feb. 14 and fatally shot 14 students, a teacher, a coach and the athletic director. Cruz, who had been expelled from the school and was arraigned on gun charges Wednesday, allegedly used a military-style semiautomatic rifle he purchased legally.

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The incident reignited the nation’s impassioned gun debate, much like earlier school shootings in Newtown, Conn., and Columbine, Colorado, and came amid heightened tensions at local schools. In addition to the San Leandro High School threat, a day earlier, Morgan Hill police arrested a teen suspected of writing a threatening message at Sobrato High School.

At Stoneman Douglas High on Wednesday, students walked out of class and onto the football field where many had fled for their lives weeks earlier. Principal Ty Thompson called for the “biggest group hug,” and the students obliged around the 50-yard line.

Students at Colorado’s Columbine High School left their classrooms for 30 seconds of silence — 17 for the dead in Parkland and 13 for the dead on their own campus in the 1999 massacre that seemed to signify the beginning of a generation of school attacks.

And in the nation’s capital, young protesters chanted outside the White House: “Hey hey, ho ho! The NRA has got to go!” Just before 10 a.m. they fell silent and sat with fists and signs held high.

In the Bay Area, students at Berkeley High School walked out in a downpour and stood in the shape of a peace sign on the football field. KPIX TV reported that at Foothill High School in Pleasanton, two students tried to stage a counter-protest during the campus walkout, while in San Jose, second grader Leonardo Aguilar was the only one to walk out of his classroom and joined the high-schoolers at Lincoln High.

Private schools also embraced the student walkout and message. St. Martin of Tours elementary school in San Jose held a prayer service in the gym Wednesday in solidarity with the national school walkout.

The walkout posed more of a challenge for public schools. Most accommodated students’ desire to express their concerns about gun violence and to remember those who died in Florida. But many tried to avoid interrupting class and to stop students from leaving campus, citing safety concerns and warning students could face penalties.

At Prospect High School in Saratoga, hundreds of students with signs like “No More Silence Stop the Gun Violence” poured out of their classrooms at 10 a.m. and gathered at the football field along Prospect Road as passing cars honked in support.

“Witnessing people our age ignite a spark back in Florida has led us to carry the torch here in California,” said junior Tasanee Reza, 16.

Hundreds of students spilled out of Evergreen Valley High School onto Quimby Road in East San Jose amid a steady drizzle, chanting “End gun violence, no more silence!”

Administrators monitored the walkout but didn’t interfere. Some students said teachers had threatened to give them no credit for missed assignments or Saturday school for an unexcused absence but that participating was worth it.

At Santa Teresa High School, principal Greg Louie sent a note to families saying that “if students leave campus, we will not restrain them, but they will receive a Saturday School referral for violating the closed campus policy.”

Chris Funk, superintendent of East Side Union High School District, encouraged school administrators to create safe places on campus for students to speak but said students need “to be clear on what they’re advocating for.”

“Organizations have their own agendas and they’re using kids as pawns,” Funk added. “I’m not saying it’s wrong, I’m just saying students need to understand what they’re walking out on.”

At John F. Kennedy High School in Fremont, students made mock tombstones noting various deadly school shootings and calling for amendments to the Second Amendment of the U.S. Constitution, which guarantees a right to bear arms.

In Florida last week, Gov. Rick Scott signed a bill raising the age to buy firearms from 18 to 21, banning “bump stocks” that boost the rate of fire for semiautomatic rifles and giving authorities greater power to seize guns from the mentally unfit. But the National Rifle Association sued to block the higher age limit for buying guns.

Gun-rights advocates note that school shootings remain rare and have urged more school security and restrictions for the mentally ill to obtain firearms. The House of Representatives on Wednesday approved a bill to fund more security at schools.

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Students at East Bay high school break through gate in gun protest ”

“These kids should be fighting for real school security, not skipping class and throwing tantrums to promote gun control laws that hurt law-abiding people,” said Brandon Combs, president of the California-based Firearms Policy Coalition.

But critics say moves to bolster school security by arming teachers only add to the danger. On Tuesday, a teacher and reserve police officer at Seaside High School near Monterey accidentally fired a gun into the classroom ceiling.

After the Prospect walkout, students heading back to class left their handmade signs perched on the fence as passing cars honked horns in approval: “We’re Not Bulletproof” and “Enough is Enough.”

Staff writers Peter Hegarty, Patrick May and the Associated Press contributed to this report.