The teacher from Mpumalanga Secondary School in South Africa was said to be monitoring grade 11 pupils writing a Tourism paper.
A video circulating on social media shows the teacher walking among pupils with what appears to be a rifle strapped over his shoulder.
No one knows his intention for carrying gun whether to protect himself from attack or to prevent students from examination malpractices unless he himself explains.
The Mpumalanga Department of Education said it suspended the teacher.
Department spokesperson Jasper Zwane said: “We have since instituted an investigation into the matter. We have [also] requested the school to open a case with the police.”
Officials will be sent to the school on Monday in order to offer counselling to the affected pupils.