Daugaard -- who signed the measure Friday -- predicted not many school districts would take advantage of the authorization and give the green light to pistol-packing teachers or so-called security sentinels from the community, The New York Times reported.
Teachers and volunteers will be required to undergo an intensive training program similar to what police officers receive.
"I think it does provide the same safety precautions that a citizen expects when a law enforcement officer enters a premises," Daugaard told the Times.
The National Rifle Association proposed armed police officers on school campuses nationwide as the best way to prevent a repeat of the Sand Hook Elementary School massacre in Newtown, Conn., in December.
Critics and advocates of gun control immediately balked at the idea of bringing more loaded guns into schools.
Proponents of the South Dakota bill -- the first of its kind in the United States -- said the idea was not particularly radical in their state where many kids are taught at a young age to hunt and handle guns safely.
The author of the bill, freshman Republican Rep. Scott Craig, said he hoped South Dakota could reassure doubters.
"It is safer than they think, it's proactive and it's preventive," he said.