Riots broke out in several French cities alongside peaceful marches of tens of thousands of people demonstrating against rising living costs and poor school conditions.

Prime Minister Sébastien Lecornu placed the blame for the chaos squarely on a far-left party, France Unbowed. The leader of that party, Jean-Luc Mélenchon, stands a chance of making the runoff in next year’s presidential election to succeed President Emmanuel Macron.

Paris — French high school students lit fires outside schools and faced off with police on Friday as a protest movement that has forced the closure or disrupted education at more than 560 establishments showed no sign of abating. The movement, which ...