Florida's House of Representatives has approved a bill allowing teachers to carry firearms - a controversial step whose effectiveness in countering school shootings remains unproven.

The aim of the measure, which was previously approved by the state's Senate and now goes to Republican Governor Ron DeSantis's desk, is the prevention of school shootings such as one that left 17 people dead at a high school in Parkland, Florida in February 2018.

Supporters of the bill - which permits teachers to carry firearms on school campuses on a voluntary basis after they have completed 144 hours of training - say armed teachers could save lives in the event of a school shooting.

But its opponents warn of the danger of accidents among teachers who would effectively be tasked with policing as well as education, and who, in the event of a school shooting, could be mistaken for a shooter by law enforcement.

"Arming teachers is a recipe for disaster - a reckless plan which will complicate active-shooter situations," Representative Val Demings, a Florida Democrat and former Orlando police chief, said of the measure.

"The real solution is to keep guns out of the wrong hands," Ms Demings tweeted.