It comes a week after the shooting which killed 17.
Thousands of protesters, including many angry teenagers, swarmed into the state Capitol of Florida on Wednesday, calling for changes to gun laws, a ban on assault-type weapons and improved care for the mentally ill.
The normally staid Florida Statehouse filled with students, among them more than 100 survivors of the February 14 attack at Marjory Stoneman Douglas High School in Parkland.
They held signs, chanted slogans and burst into politicians' offices demanding to be heard.
The teens were welcomed into the gun-friendly halls of power, but the students' top goal — a ban on assault-style rifles such as the weapon used in the massacre — was taken off the table a day earlier, although more limited measures are still possible.
Many protesters complained that politicians were not serious about reform, and they said they would oppose in future elections any legislator who accepts campaign contributions from the National Rifle Association.
"We've spoke to only a few legislators and … the most we've gotten out of them is, 'We'll keep you in our thoughts. You are so strong. You are so powerful,'" said Delaney Tarr, a senior at the high school.
About 30 people left an anti-gun rally outside Florida's Old Capitol and began a sit-in protest at the office of four House Republican leaders, demanding a conversation about gun legislation.
"They're not speaking to us right now. We only asked for five minutes and so we're just sitting until they speak," Tyrah Williams, a 15-year-old sophomore at Leon High School, which is within walking distance of the Capitol.
At a town hall meeting held by CNN in Sunrise, Florida, on Wednesday night, thousands of angry students, teachers and parents booed Republican Senator Marco Rubio when he indicated that he would not support an assault-weapons ban and applauded Democrat Representative Bill Nelson when he pushed Mr Rubio to work on a bill that they both could support.
They also booed a spokeswoman from the NRA when she said the answer was not to ban weapons but to ensure they stay out of the hands of the mentally ill.
"How is it possible that this boy that we all knew was clearly disturbed was able to get an assault rifle, military grade, and come to our school and try to kill us?" one 16-year-old student asked the president of the state Senate, Joe Negron.
Mr Negron did not answer directly. "That's an issue that we're reviewing," he said.
When another politician said he supported raising the age to buy assault-style weapons to 21 from 18, the students broke into applause.
Florida politicians have rebuffed gun restrictions since Republicans took control of both the governor's office and the Legislature in 1999.
Saying the tragedy at the high school was "completely unavoidable," Republican legislative leaders say they will consider legislation that will likely call for raising the age limit to purchase a rifle in Florida and increasing funding for mental health programs and school-resource officers, the police assigned to specific schools.