The women arrived at a school in Andernos-les-Bain early on Monday afternoon bearing what appeared to be an automatic firearm, reported the Sud Ouest newspaper.
They casually asked other students for cigarettes, without trying to hide the fact that they were apparently armed.
Students wasted no time in alerting authorities, who sent several dozen police officers and one helicopter to the scene - but by the time they got there the women had vanished.
Meanwhile, the school children were locked in the classrooms as police spent the next four hours searching for the suspects. The tweet below from a local newspaper says 850 students were kept inside the school.
Officers eventually found the pair - both in their early 20s - at the home of one of the women and hauled them in to the police station.
Police have launched an investigation into what it called "reckless behaviour".
Local media, meanwhile, concluded that it was nothing more than a prank - and if indeed this is the case, the tasteless stunt couldn't have come at a more sensitive time.
Just three weeks ago, terrorists armed with Kalashnikovs killed 130 people in a spate of attacks across Paris. France has been in a state of emergency ever since with the terror alert level at its highest.