PARIS (Reuters) - French police fired tear gas on Thursday at youths who hurled projectiles and vandalized property on the fringes of a student demonstration against the alleged rape of a young black man by police using a baton.

Hundreds of high-school students blocked the entrances to more than a dozen schools in Paris during the unauthorized rally which was largely peaceful aside from the isolated skirmishes. Police made 26 arrests.

The protest comes two months before a presidential election in which opinion polls show far-right leader Marine Le Pen performing strongly on an anti-immigration, nationalist platform.

It was the latest in a series of demonstrations against the alleged police mistreatment of a 22-year-old man identified only as Theo, who remains in hospital with injuries to his anus and head.

One banner at Thursday’s rally read “Revenge for Theo!”

He has called for public calm and his family has said they have faith in the French justice system.

The Paris school authority said more than 10 schools had been targeted by youths who piled up rubbish bins and other objects at the entrance gates. In one case, a deputy school director was injured when protesters hurled a fire extinguisher.

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Education Minister Najat Vallaud-Belkacem said she understood young people’s “emotion” over the Theo case but called for public calm and denounced the violence.

“I am appealing for calm because excesses like this, violence and blocking entrances to places, are not acceptable. The state will show considerable firmness,” she said on Public Senat TV.

Video footage on social media showed a confrontation on the fringes of the rally in the Place de la Nation square in the east of Paris, where riot police in protective gear advanced on groups of mostly-hooded youths in sidestreets.

A helicopter flew overhead and tear gas clouds rose into the air above that square towards the end of the rally.

The Paris police department had warned people to stay away from the protest, saying there was a risk of violent groups causing trouble, as happened over the last three weeks.

Four police officers have been suspended pending an inquiry into the Feb. 2 incident. One has been placed under formal investigation for suspected rape and three others for unnecessary use of force.

So far the protests have not snowballed to the extent of the unrest that 12 years ago drew global attention to the stark contrast between wealthy Paris and the suburbs that surround it.