Demonstrators clashed with police when hundreds gathered at the city's Place de la Sorbonne square in the Latin quarter following a protest march.
Protesters vandalised cafes as police repelled them with teargas and water cannon that left the area veiled in pungent fumes.
A bookshop was set on fire in the square along with a car near departments of the Sorbonne University and police said 35 officers were injured, nine of whom were treated in hospital.
About 257,000 people took to the streets in up to 80 towns and cities across France, while some organisers set the figure as high as half a million.
Student leaders said that 120,000 people joined the march through Paris's Left Bank university quarter, although police said there were 30,000.
Other regions
Outside Paris, two officers and a student were slightly injured in scuffles pitting police against some 250 high-school students, heading to the Paris march from the northern suburb of Raincy.
Large rallies were also held in Marseille, Lyon and Grenoble in the south and southeast, Bordeaux in the southwest, Rennes and Lille in the northwest and north, Clermont-Ferrand, Limoges and Angers in the centre and Strasbourg in the east.
Similar scenes of violence erupted last week when riot police were called in to evacuate demonstrators from Paris' historic Sorbonne University.
The interior ministry reported 212 arrests across the country, including 147 in Paris alone.
Cause of protests
The protests were organised in anger at the proposed First Employment Contract (CPE), which the government says will encourage youth employment.
Opponents of the reforms say the CPE, which can be broken off without explanation in the first two years, is a licence to hire and fire at will, and are demanding its withdrawal.
Prime Minister Dominique de Villepin, who championed the scheme as a key tool in fighting youth unemployment, faces the most serious test of his premiership as the wave of protests paralyses dozens of French universities.
Unions have called for a further day of protest on Saturday, when the head of the powerful CGT union, Bernard Thibault, has vowed to "step up a gear" in the stand-off with the government.