President Emmanuel Macron caused surprise on the campaign trail in 2017 by promising to introduce a month-long compulsory national service, saying he wanted to give girls and boys "a direct experience of military life".
The proposal got a cool response from the army, which baulked at the prospect of having to put millions of teens through their paces, prompting the government to come back with proposals for a compulsory civic service instead.
Some 2,000 youngsters were chosen out of 4,000 volunteers for the first part of the trial, which start on Sunday at boarding schools, holiday villages and university campuses across the country.
For a fortnight, the 15 and 16-years-old will leave home for training in first aid and other basic skills, followed later by another two weeks of volunteering.
Navy uniforms and national anthem
Each volunteer will leave home for another region for the two weeks, during which they will be required to wear navy uniforms and sing the Marseillaise, France's national anthem, every morning.
Described as an "integration phase", the teens will be taught first aid, map reading, and other skills.
A second two-week phase, later this summer or during the coming school year, involves work on a "collective project", such as volunteering with a charity or local government.
Patriotism and social cohesion
Macron has billed the service as a way to develop patriotism and social cohesion in a country battling deep divisions between left and right, rich and poor, and religious and non-religious.
The programme, which will be written into the French Constitution, will be rolled out over the next seven years, targeting about 800,000 youngsters per year, eventually becoming compulsory.
France requires all citizens to participate in a one-day "Defence and Citizenship" course when they turn 18, which includes a presentation of the country's military forces and a French language test.
Macron is the first French president not to have been called up to serve, having come of age after the compulsory 10 months of military service for school-leaving men was abolished by ex-president Jacques Chirac in 1997.