France is Missouri’s mirror image: the same schedule, adopted for opposite reasons, and argued about on entirely different grounds.
The Darcos decree of May 2008 abolished Saturday-morning classes and put every French primary school on four days — 24 hours of instruction across Monday, Tuesday, Thursday, and Friday. Nearly every school moved within two years. A 2013 reform under Vincent Peillon pushed schools back to 4.5 days, restoring Wednesday mornings and leaving communes to fund the afternoon activities that replaced the lost class time. Mayors and parents disliked it, and a June 2017 decree let communes opt back out. They stampeded: 43 percent of communes were back on four days that autumn, 87 percent within a year, and about 93 percent by 2023. The holdouts are the big cities — Paris, Toulouse, Lille.
The result is the developed world’s most extreme school calendar: roughly 144 instruction days a year, packed into six-hour days. That number is the single most misunderstood figure in the international comparison, and it is worth the detour below.
What France knows that America doesn’t.
France ran the experiment America never ran. A half-century of French chronobiology — Testu’s work on children’s daily performance rhythms, the 2001 INSERM collective expert review, the Académie nationale de médecine’s 2010 position — concludes that the four-day week desynchronizes young children. Under a four-day schedule the normal daily attention curve inverts, with depressed vigilance on Monday and Tuesday; under 4.5 or five days that effect is largely confined to Mondays. The Académie’s 2010 verdict was blunt: the four-day week “n’est pas favorable à l’enfant.”
This body of work is essentially uncited in the American four-day debate. It is the strongest child-development argument against the schedule anywhere, and it comes from the only country running the schedule at national scale.
What America knows that France doesn’t.
France never measured achievement. When the Sénat examined the school-rhythms reforms in 2017, the head of DEPP — the French education ministry’s research arm, roughly its DESE equivalent — told senators that the way the 2013 reform had been rolled out made scientific evaluation impossible, because there was no comparison group. The inspectorate called it the astonishing paradox of a reform that gave itself no means of evaluating itself.
So the American literature’s estimates of achievement, teacher retention, and juvenile crime have no French counterpart, and the French chronobiology has no American counterpart. Each country ran half the experiment.
The politics rhyme.
French teachers strike for the four-day week — Rennes did so in May 2025. Communes prefer it because the 4.5-day version left them paying for Wednesday-morning childcare and afternoon programming, on the order of €160 net per child per year. And the sharpest French critique is one American parents will recognize: a free weekday advantages families with money and flexible schedules, and lands hardest on working mothers.
What happens next.
In May 2025 the president empaneled a citizens’ convention on children’s time — 133 randomly selected citizens plus 20 children. In November 2025 it adopted, by a large majority, a recommendation to move French primary schools back to five days, Monday through Friday, on explicitly chronobiological grounds: “les chronobiologistes sont unanimes.” The government has not acted. In February 2026 the education minister ruled out any change for the coming school year; in April 2026 he called the school-week question “typiquement un sujet de présidentielle 2027” — a matter for the 2027 presidential campaign. Paris launched its own convention in May 2026.
France is, in other words, seriously considering abolishing the schedule that American districts are adopting — and for reasons American districts have never studied.