Teachers in schools in South Dakota could be allowed to carry guns after the state voted to allow 152 school districts to decide if they want to arm school staff.

The "school sentinels" bill was introduced after the Newtown shootings in Connecticut. School boards must get approval from local police, and sentinels would have to be trained carry weapons in the schools. District residents could put the issue to a referendum.

Friday's vote in South Dakota follows a proposal in Georgia to extend the right to carry arms. The Republican-led state house voted 117-56 on Thursday to allow licensed gun owners to take weapons inside some unsecured government buildings where they are currently banned, starting on July 1. They would still be outlawed from college dormitories and sporting events.

The Democratic state representative Karla Drenner, who opposed the measure, said it was part of a backlash against a national push to strengthen gun control laws after the murder of 26 children and adults in Connecticut.

Drenner, an instructor at several colleges, said she was concerned about the impact on potential confrontations with angry students, recalling on Friday how a student once screamed at her for mispronouncing his name.

"If he had a gun, the outcome could have been much different," Drenner said.

In more liberal states with large urban centres such as New York and California politicians have been introducing more stringent gun control laws, but more conservative rural areas have been going in the opposite direction.