Hundreds of pupils in southern France headed to school in uniforms for the first time on Monday as part of a national experiment to determine whether to make them compulsory.
Uniforms have never been required in state schools in mainland France.
But centrist President Emmanuel Macron last month announced a uniform trial at around 100 schools, with a view to making them mandatory nationwide in 2026 if it is successful.
Towns run by the right wing make up the majority of those that signed up for the test, though some have met strong resistance from teachers, students and parents.
Critics say the money would be better spent in other areas of public education to improve learning.
Around 700 students at four schools in the southern town of Beziers appeared to be the first to try it out in mainland France on Monday.
A school had given identical outfits a go in the overseas territory of La Reunion last month.
In the schoolyard of one primary school, seven-year-old Alexia said she hoped for fewer comments from classmates about her appearance while wearing her new dark blue uniform.
"Sometimes they'd say, 'you're ugly, we're not dressed the same'. It was a bit hurtful," she said.
Now "at least we'll have the same skirt, the same top, the same jacket."
Pupils in Beziers, a town with a far-right mayor and a high unemployment rate, had been invited during half term to come with their parents to pick up their outfits.
The city and national governments are sharing the 200-euro ($216) cost of each uniform, made up of a blazer with the school's logo, two polo shirts and one pair of trousers, as well as a pair of shorts or a skirt depending on gender.
Mayor Robert Menard said the move would help fight bullying.
"When you're rich or poor, you don't dress exactly the same way," he said. Now "it will be less visible."
But the SE-UNSA teachers' union slammed the measure as a "superficial response to a fundamental problem", adding it would "in no way help resolve the troubles and failures of students".
- 'Peaceful climate' -
Education Minister Nicole Belloubet said that so far 92 schools had volunteered to try out a uniform, including towns outside Beziers that had been "more discreet" about it.
"What we would like to see is if, yes or no, wearing a uniform can create tranquillity in classrooms," said the minister.
"We know you learn better in a peaceful environment."
Schools have until June to sign up to the initiative.
Those who have rejected it include a middle school in the southern city of Marseille.
The wider Bouches-du-Rhone region -- whose head hails from the right-wing Republicans party -- had approved the trial, but 66 percent of pupils at the Marseille school voted against it, according to a letter to parents seen by AFP.
In the western village of Plouisy, parents last month staged a protest when they heard the mayor, from Macron's Renaissance party, had signed up for the test. The idea was dropped.
First lady Brigitte Macron, a former drama teacher, has backed the introduction of school uniforms.
Far-right former presidential candidate Marine Le Pen has also supported a compulsory dress code.