(CNN)Nearly 20% of the student population didn't show up Wednesday at Marjory Stoneman Douglas High School after two fellow students were charged with bringing weapons to campus, another made a threat of violence on social media and a security guard was found asleep in his car.
Many said they had already planned to take the day off to prepare for their trip to Washington, on Thursday, ahead of the March for Our Lives rallies planned for Saturday. Friday is a teacher workday at the high school in Parkland, Florida, giving students an extra day in their spring break, which goes through April 1.
Watch students walk out of schools across US 01:36
But others are staying away due to the stress and fear they still feel more than a month after 17 people were killed at the school by a former student -- especially after the arrests Tuesday, and the fact that the gunman's brother, Zachary Cruz, was allegedly caught trespassing on the Stoneman Douglas campus on Monday. He appeared in court Tuesday for that offense.
See school officer outside during shooting 02:11
Out of a student population of roughly 3,280 students, 724 were absent first period Wednesday and 646 were absent second period, according to Broward County Schools spokeswoman Nadine Drew; that's about 21.9% and 19.5% of the student body, respectively.
CNN reporters and producers have been talking and corresponding with some students on social media. Here's what they're saying about their decision to go -- or not go -- to school.
Sammy Feuerman, 17, senior
Feuerman, whose best friend, Joaquin Oliver, died in the February 14 massacre, was among those who didn't go to school. He's not sure it's safe enough to go back yet.
"I need to see it to believe it, that's when I go back," he said about security measures at Stoneman Douglas.
911 calls reveal first few minutes of shooting 02:40
Jack Macleod, 16, junior
Macleod did go to school, but was late.
"I definitely feel even less safe than I did before. It's absolutely ridiculous," he said.
"I feel pretty upset. They piled the campus with cops the days we first came back, but no one was in danger. Then this cop falls asleep, and a (student) threatens someone with a knife, someone hops the fence, and someone posts threatening Snapchats. I don't think that the cop falling asleep is connected, it just annoys me."
Two injured in Maryland school shooting 01:00
After hearing about the school shooting in Maryland on Tuesday in which that school's resource officer contained the student gunman, he said he feels like "something is wrong with law enforcement right now." The resource officer at Stoneman Douglas the day of the shooting was suspended after he failed to confront the gunman, though the officer's attorney said he didn't know exactly from where the gunshots were coming.
Judge enters not guily plea for Nikolas Cruz 01:41
Kevin Trejos, 18, senior
Trejos, who went to school, said he doesn't understand why anyone thinks it's a good idea to bring a knife to school.
"We are clearly told it's not allowed, whether it's a paring knife or a knife for security."
Kevin Trejos shared this photo of the first day students went back to school after the mass shooting.
He also feels like the resource officers at his school "have dropped the ball."
"I often saw them conversing among themselves or being practically asleep in their cars. Up until now, they were not even checking the people who were coming in through the other exits, they just let us walk in without question."
Demitri Hoth, 18, senior
Hoth had already planned to stay home Wednesday to prepare for his trip to Washington.
Demitri Hoth
When asked how he felt about security at school before the shooting, he said, "It's scary to know that at any given point in time a person can come onto campus and just hurt somebody."
Connor Deitrich, 17, junior
The students are on edge at school, Deitrich said. He decided to attend school but the atmosphere is tense.
"I mean, we're all just going about our usual day trying to get through the school day, but security is upped and a lot of media is back, so it was kind of nerve-racking coming into school."
As for the report about the deputy sleeping on the job, he said, "A lot of us are angry that we were failed twice now by school officers."
Kai Koerber, 16, junior
"Things have an atmosphere of immense tension," he said Wednesday after he got to school.
"We understand that police protection is absolutely necessary given what we experienced, but nevertheless, a tremendous police presence in a place of learning where everyone is supposed to feel safe makes everyone uneasy. We are all at a crossroads between feelings of security and fear."
Julia Salomone, 18, senior
She and her sister almost didn't go to school, Salomone said.
"But we pushed through and are trying to make it through the day. It's hard to not let fear rule your life when constant reasons not to feel safe keep appearing."
"Things feel tense -- students already feel uncomfortable being in school. We already don't feel safe because of what happened, and recent events just add to the fear we already have."
Jeff Foster, AP government teacher at Stoneman Douglas
Foster said he heard at a rally Tuesday night that a lot of kids were planning to stay home.
"Kids aren't scared, they are just tired of all this. (They) want to get back to normal. Spring break is coming at the right time!"
The teacher said the majority of his students are headed to the march in Washington and are really looking forward to time away.
Rebecca Boldrick, mother of students David and Lauren Hogg
Student to lawmakers: We're children, you are the adults 00:45
Boldrick said her daughter, Lauren, stayed home. Lauren lost four friends in the February 14 shooting.
"I wasn't comfortable with her going to school today, but she was insisting. And then when we were driving to school and the helicopter was flying over, she decided she didn't want to go, saying she felt like her school was a prison."
Shooting survivor: How many more have to die? 01:32
Tuesday was a crazy day at school for Lauren, her mom said.
"Since they arrested Nikolas Cruz's brother for trespassing last night and the principal told us they did an entire bomb sweep of the campus, there were helicopters overhead all day, causing extreme anxiety to kids like my daughter. She associates the sound of a helicopter with the shooting."
Superintendent sends letter to parents
Broward County Public Schools Superintendent Robert Runcie on Wednesday sent a letter to school district families concerning safety concerns and the district's efforts to expand safety protocols.
He said the district is upgrading real-time surveillance camera systems at all schools, is asking law enforcement agencies to evaluate protocols for drills and is moving toward having a single point of entry for campus visitors.
"While we cannot change the heartbreaking and senseless act of violence at Marjory Stoneman Douglas, by working together, we can change the future. All students deserve safe schools," Runcie wrote.
