Thousands of schoolchildren went on the rampage after rumours spread that President Nicolas Sarkozy's government wants to take away a large slice of their school holidays.
Protests that began in northern France spread to the capital's outskirts on Friday, where police said they arrested 10 people after high-school students rioted, damaging cars by turning them on their side or smashing windows.
Another 18 were arrested in northern France, where protesters attacked buses, torched bins and allegedly insulted a police officer.
About 20 schools were affected in the Picardy region north of Paris, including in Amiens, where pupils set fire to bins and threw stones, eggs and tomatoes.
Four youths were arrested near a school in Amiens after a Molotov cocktail and bricks were thrown. Police said the suspects were "people from outside come to make trouble".
