Those who were in the cafeteria had to put down their cutlery, the others put down their pen or desert the courtyard.
The multi-purpose Rive Gauche high school in Toulouse, which hosts 1,600 students, was completely evacuated at midday after a fire broke out in a basement.
The firefighters were called around 1:07 p.m., first because of a significant release of smoke.
Some 25 firefighters from three barracks were deployed to the scene.
They contained the fire, which started in an archive room.
But at the beginning of the afternoon, they were still on site to ventilate the buildings and clear the area destroyed by the flames.
The fire caused no injuries in the school community.
The rectorate of Toulouse indicates that the establishment will remain closed this afternoon to allow time for the premises to air out and for the firefighters to continue their inspection.
The school will reopen this Tuesday evening for interns and Wednesday morning for all other students.
In Toulouse, major fire in a Mirail building
A squatted house partly destroyed by a fire in Toulouse