The young Muslim pupil at a high school in Seine-Saint-Denis in the northern suburbs of Paris, says he has been growing his beard out for two years.
But the facial hair is not to the liking of the school's headmaster, who reportedly asked the pupil to trim it back.
“I explained that I grew it for religious reasons, and he said it was a sign of radicalization and told me: You cut it or you leave,” the student told Le Parisien newspaper.
There are no rules against pupils having beards, and the 21-year-old was quick to point out that he wasn't alone in having one.
“I'm not the only one with a beard, there are teachers and students that have them,” he said. “It's important to me, the Prophet [Mohammed] had one,” he said.
The bearded pupil said that he has since told the headmaster that he would be dropping out of the school.
Educational authorities have denied there was any issue around beards or an ultimatum from the headmaster.
The issue of demonstrating signs of religion openly is a touchy issue in secular France.
France imposed a ban in 2004 on pupils being able to display any religious items such as the hijab veil worn by Muslim women, but there was no mention of beards.
Schools in France have cracked down on other fashions of late that have been deemed “too religious”, even though they're not against the dress codes.
In May a teenage Muslim girl was barred from entering her school grounds for wearing a long black skirt seen as too openly religious.
The headmistress reportedly deemed that the skirt “conspicuously” showed religious affiliation, which is banned in schools by France's strict secularity laws.
Teachers and school staff are under pressure to report signs of radicalisation among pupils to police.
Earlier this year the education minister said that the names of hundreds of pupils had been passed on.