Non French, non European Union students are often required by French consulates to provide proof of their health insurance when they submit their visa application.
Indeed, students must be covered by their own insurance prior to the beginning of their course in France.
For example: John is enrolled in Grande Ecole MSc, the starting date of which is scheduled on 27 August. To settle smoothly, John has booked a flight landing at Roissy Charles de Gaulle airport on 22 August. On his way out of the airplane, John falls and breaks his leg. He has to be rushed to the nearest hospital. John's medical expenses should be covered by his personal insurance because the French Social Security scheme becomes effective only after the start of his course.
Jane, on the other hand, also enrolled in Grande Ecole MSc, catches a terrible cold early September a couple of weeks after her arrival from Mexico. Her medical expenses should be covered by the French Social Security scheme once she has registered online on Social Security platform.