The measure will automatically become law within 15 days unless vetoed by Governor Rick Scott, a Republican.
Florida state lawmakers gave final passage on Wednesday to a gun-safety bill that would raise the legal age for buying rifles, impose a three-day waiting period on all firearms sales, and allow the arming of some public school employees.
The package was spurred by the shooting rampage three weeks ago that killed 17 students and faculty members at Marjory Stoneman Douglas High School in Parkland and led to an extraordinary lobbying campaign by young survivors of the massacre.
But the legislation, while containing a number of provisions student activists and their parents had embraced, left out one of their chief demands - a ban on assault-style weapons like the one used in the February 14 massacre.
Supporters defended the bill, saying that most school shootings, which have occurred with a frightening frequency in the United States during the past few years, are committed with handguns.
The measure will automatically become law within 15 days unless vetoed by Governor Rick Scott, a Republican. A spokeswoman for Scott said on Tuesday he had not yet decided whether to support the bill.
The bill overcame strenuous objections to provisions permitting school staff to carry guns on the job. Critics see that as posing a particular risk to minority students who they say are more likely to be shot in the heat of a disciplinary situation or if mistaken as an intruder.
Swift action in the Republican-controlled statehouse, where the National Rifle Association (NRA) has long held sway, signalled a possible turning point in the national debate between gun control advocates and proponents of firearms rights enshrined in the Second Amendment of the US Constitution.
The measure narrowly cleared the state Senate on Monday before passing in the House of Representatives on Wednesday in a 67-50 vote. Ten House Democrats joined 57 Republicans in supporting the bill, while 19 Republicans and 31 Democrats voted against it.
As legislators debated in Tallahassee, US Education Secretary Betsy DeVos visited Stoneman Douglas on the first full day of classes since the shooting, while a Broward County grand jury indicted accused gunman Nikolas Cruz on 17 counts of premeditated murder.
The action by Florida's lawmakers represented both a break with the NRA on gun sale restrictions and a partial acceptance of its proposition that the best defence against armed criminals is the presence of "good guys with guns."
The bill would create a program allowing local sheriffs to deputize school staff as volunteer armed "guardians," subject to special training, mental health and drug screening and a license to carry a concealed weapon. Each school district would decide whether to opt in.
Nearly all classroom teachers are expressly excluded from participating in a compromise aimed at winning support from some Democrats and Scott, a staunch NRA ally who nevertheless is opposed to arming teachers. Otherwise, only non-teacher personnel are eligible, such as administrators, guidance counsellors, librarians and coaches.
Florida would join at least six other states - Georgia, Kansas, South Dakota, Tennessee, Texas and Wyoming - with laws allowing school employees to carry firearms at kindergarten-12 public schools, according to the National Conference of State Legislatures.
President Donald Trump has voiced support for arming teachers as a deterrent to school gun violence, though many parents, law enforcement officials and policymakers in both parties reject the idea.
"The thought of even one student being gunned down by the person responsible for educating and caring for them is just too much," Representative Amy Mercado, a Democrat from Orlando, said during the House floor debate.
A Scott spokeswoman has said the governor would review the bill in its final form before deciding whether to support it. Scott's concerns also include the proposed three-day waiting period for purchases of all firearms. Florida currently applies a three-day wait only to handgun sales.
Another key provision would raise the minimum age for all gun purchases in the state to 21. The minimum age for handguns nationally is 21, but a person as young as 18 can buy a rifle in Florida.
Cruz was 18 years old when he legally purchased the semiautomatic AR-15 assault-style rifle used in the Stoneman Douglas massacre, according to authorities.
The measure also makes it easier for police to temporarily seize guns from people involuntarily committed due to mental illness or deemed a danger to themselves or others by a court.
Cruz had a history of mental issues, numerous encounters with police and was expelled from Stoneman Douglas in 2017 for disciplinary problems, according to authorities.