The "National School Walkout" slated to begin Wednesday at 10:00 am (1400 GMT) will last 17 minutes -- one for each victim shot dead during the Valentine's Day massacre in Parkland.
Watch live video, courtesy of ABC News, below:
The event to honor those slain at Marjory Stoneman Douglas High School is also an act of protest against the firearms violence plaguing the United States, which has more than 30,000 gun-related deaths annually.
Organizers come from the same group behind the Women's March, which in January 2017 saw millions of demonstrators take to the streets against Donald Trump's White House inauguration.
Those launching calls for action, many under the hashtag #Enough, are urging measures including expanding the background check system for gun purchases and curbing sales of assault-style rifles.
"Students and staff have the right to teach and learn in an environment free from the worry of being gunned down in their classrooms or on their way home from school," organizers wrote on their website.
"We are not safe at school. We are not safe in our cities and towns. Congress must take meaningful action to keep us safe and pass federal gun reform legislation," the said, referring to "the public health crisis of gun violence."
The #Enough movement has also voiced resolute opposition to arming school staff members as a means of defense against future shootings.
Some staunch defenders of gun access floated that proposition in the wake of the Florida bloodbath -- and just last week the southeastern state's governor signed into law a measure that would pave the way for such a system, which Trump also favors.
Both the White House and Congress have shied away from putting forth major reforms on gun sales.
The Parkland shooter used an AR-15 military-style rifle, a type now being targeted by activists, who are also against high-capacity magazines.
Florida prosecutors announced their plans to seek the death penalty against the accused Florida gunman Nikolas Cruz, for 17 premeditated murders.
The 19-year-old shooter is due to appear in court Wednesday to be formally charged. His lawyers have indicated he would accept to plead guilty in exchange for guarantees that he would not face capital punishment.
- Disciplinary threat -
Trump had momentarily signaled support for increasing restrictions, but now stands accused of bowing to the US gun lobby.
A new policy statement emphasized the US president's motion to arm school personnel would make "sure our schools are safe and secure, just like our airports, stadiums and government buildings."
It did not, however, mention new federal gun purchasing age limits or expanding firearms vetting.
The US has seen a spate of fatal school shootings in recent years, as well as mass shootings in other public places.
Some parents and teachers have said protesting around the sensitive issue could be particularly traumatic for America's youngest.
To prepare for Wednesday's planned walkout, organizers fostered debate among students of various ages to discuss forms of expression like rallies and posters, as well as slogans.
One Texas district warned that school authorities would slap any student who walked out with a three-day suspension.
"We will discipline no matter if it is one, fifty, or five hundred students involved," said the Needville schools superintendent in a statement widely published on US media. "A school is a place to learn and grow educationally, emotionally and morally."
"A disruption of the school will not be tolerated."
Sarah Hinger of the American Civil Liberties Union -- an organization working to protect constitutional rights including the right to free speech -- called that stance a "missed educational oportunity."
The superintendent of schools Broward County, the area where the Parkland shooting occurred, also described the walkouts as "teachable moments" and said they demonstrate students' right to freedom of expression.
In another symbolic move, 7,000 pairs of shoes were placed in front of the US Capitol building in Washington to represent the children killed by firearms since the Sandy Hook Elementary School shooting in December 2012 in Connecticut.
