Supporters say the so-called sentinels could help prevent tragedies such as December's shooting at Sandy Hook Elementary in Newtown, Conn., in which 20 students and six teachers died. The law will go into effect July 1.
The bill's main sponsor, Rep. Scott Craig, R-Rapid City, said he started working with federal law enforcement officials on the measure in early November, and the Connecticut tragedy weeks later "only affirmed the rightness of this bill." He said the measure does not force a district to arm its teachers or force teachers to carry a gun.
"There's no mandating of anything. It's provisional. It's a take-it-or-leave-it bill," he said.
South Dakota doesn't stand alone on this issue. For a dozen years, Utah has allowed teachers and others with concealed carry licenses to wear a gun in a public school. A couple of school districts in Texas have been given written authorization to allow guns in schools. And legislatures in other states, including Georgia, New Hampshire and Kansas, are working on measures similar to South Dakota's.
Several representatives of school boards, school administrators and teachers opposed the bill during committee testimony last month. They said the measure could make schools more dangerous, lead to accidental shootings and put guns in the hands of people who are not adequately trained to shoot in emergency situations.
Rob Monson, executive director of School Administrators of South Dakota, said his group opposes the bill because it fails to address key issues, such as school building safety, mental health and fire and emergency response.
"We were really hoping that they would look at doing a more comprehensive study of school safety overall, and not sort of jump right into arming people in our schools and thinking that is the answer to it all," Monson said.
But Craig said a number of school board members and administrators voiced support for the bill.
"There are plenty of school districts that let us know that they've wanted this, and they've wanted this kind of provision for quite some time," he said.
On Monday, the South Dakota House voted 40-19 to accept the Senate version of the bill, which added a requirement that a school district must decide in a public meeting whether to arm teachers and others. Another Senate amendment allowed school district residents to push a school board's decision to a public vote.
Craig said he couldn't say how a typical district would implement a sentinel policy, as those decisions will be made locally.
"They get to work out the details in the days ahead," he said. "They've just kind of been waiting and watching to see if this even would pass."
Monson said school districts are going to want to know how the bill's passage will affect them.
"Our biggest challenge right now will be answering all the questions that school boards and administrators are going to have about liability issues and all the other pieces that haven't been put in place yet," Monson said.