RICHMOND, Va. — Virginia Attorney General Mark Herring is warning a rural school district that its plan to arm teachers is unlawful.

Herring's office released an opinion Tuesday saying the school board in Lee County should not proceed with its plan to let an undisclosed number of teachers and staff members carry guns in school.

The board voted in July to arm teachers, saying it's a cost-effective way to protect against school shootings. The board wants school employees who carry guns to be designated as "special conservators of the peace" to try and exempt them from state law prohibiting guns in schools.

But Herring, a Democrat, said this board's plan is still prohibited by law and arming teachers would make schools less safe.