About 400 students and more than 100 teachers at Plainview - Old Bethpage John F. Kennedy High School participated.
School district officials said the walkout lasted 21 minutes, representing the 21 people students and teachers killed in the Texas school massacre last week.
It was a day to connect with the young children -- not just numbers -- but the lives cut short in Uvalde last week.
As the choir sang, students wondered how many more lives it will take. Some began to cry.
"I'm just like, sad that we even have to be here and doing this just to get our voices heard," high school senior Amy Brickel said.
"And there's a feeling of - this is gonna happen again, this isn't a case study, this isn't something that is isolated," high school sophomore Yoav Muscal said.
Organizers wanted this walkout to show that students can do something.
"We can vote. I mean, I'm 18 now so half my grade is now able to vote," walkout organizer Ashlyn Woo said.
They are well aware of the issues surrounding school violence and the challenge facing their generation of trying to find any common ground.
"There's mental health angle from the perpetrators, what mental health issues are they struggling with, and then there's the side of the schools themselves, increasing security, and then of course there's the other side, of stricter gun legislation," senior Jessica Knaster said.
Their teachers and administrators joined them on Wednesday. All of the teens have grown up with Sandy Hook, then Parkland and now this Uvalde.
"It's been extremely frustrating for them, they're angry hurt, heartbroken for the loss of their peers," Jim Murray said.
While hundreds turned out, it's really about who is not here and what's become their new curriculum.
"Like we had to choose a topic to do a research paper on and I did it on gun shootings, especially school shootings and it's just hard," Brickel said.
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