A year ago, in the wake of horrific tragedy, Florida lawmakers reached a compromise that had once seemed politically impossible: they passed an array of gun restrictions after a young man killed 17 people at Marjory Stoneman Douglas High School in Parkland.

Part of that compromise allowed certain school employees, but not classroom teachers, to carry firearms on campus.

Then, late last year, a state commission investigating the Parkland shooting came to a conclusion that made even some of its members uncomfortable: Some of the deaths at Stoneman Douglas High might have been prevented if faculty inside the building had been armed.

Based on that conclusion, state lawmakers are now poised to lift Florida’s ban on arming classroom teachers, allowing them to receive the same voluntary training as other staff to carry weapons in school. On Tuesday, the state Senate approved the change, which now heads to the more conservative state House for what is expected to be final passage.

Florida shooting – in pictures Show all 10 1 /10 Florida shooting – in pictures Florida shooting – in pictures Police arrest a suspect in connection with the shooting at the Marjory Stoneman Douglas High School in Parkland, Florida Reuters Florida shooting – in pictures Parents wait for news after reports of a shooting at Marjory Stoneman Douglas High School in Parkland, Florida AP Florida shooting – in pictures Anxious family members wait for news of students AP Photo/Wilfredo Lee Florida shooting – in pictures Students being evacuated from the school AP Florida shooting – in pictures Students being evacuated from the school Getty Florida shooting – in pictures People gather waiting for word from students AP Florida shooting – in pictures Parents waiting for news on their children AP Florida shooting – in pictures People gather at a hotel where students were taken after the shooting Getty Florida shooting – in pictures Florida Governor Rick Scott speaks to the media as he visits Marjory Stoneman Douglas High School following the shooting AFP/Getty Florida shooting – in pictures Dr. Igor Nichiporenko, Medical Director Trauma, left, and Dr. Evan Boyer, Medical Director, Emergency Services, speak about treating victims and the suspect at a press conference outside Broward Health North hospital AP

Some parents and students from Parkland who have become activists against gun violence are steadfastly opposed to the change. They travelled to the state Capitol in Tallahassee in recent weeks to protest against the expansion of the so-called school guardian program, saying more guns on campus would put children in more danger. The National Rifle Association has sought to arm Florida teachers for years.

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About 150 students with the March for Our Lives movement descended on the Capitol in buses earlier this month; they forced a delay in a House hearing — but no more. There was no similar demonstration against the legislation when the Senate took it up Tuesday.

Still, the vote proved wrenching for Senator Lauren Book, a Democrat from the city of Plantation, near Parkland, who sat on the state commission investigating the school shooting and favoured the recommendation that districts allow teachers to be armed.

But, through tears, she said she could not vote for the provision on the Senate floor, citing the intense opposition from the Parkland community. She called the vote “exceedingly painful.”

The 22-17 Senate vote fell almost entirely along party lines, with a single Republican, Senator Anitere Flores of Miami, joining all of the chamber’s Democrats in voting against the bill.