France's prestigious Institute of Political Studies doesn't take kindly to students skipping class — but it was OK when nearly the entire student body of 5,000 didn't show up one day. 

Students declared Thursday a "dead day" and stayed away from classes so they could march against ultra-right leader and presidential candidate Jean-Marie Le Pen. 

Across France, protesters by the tens of thousands have been taking to the streets to chant slogans against Le Pen every day since Sunday, when the anti-immigration firebrand came in second in the presidential primary after conservative incumbent President Jacques Chirac. Chirac and Le Pen face off in a May 5 final. 

The first demonstration erupted spontaneously just hours after the results of the primary were declared, when thousands of people from leftist parties poured into central Paris to denounce Le Pen's victory over Socialist Prime Minister Lionel Jospin, who came in a humiliating third and was disqualified from the race. 

Jean-Dominique Giuliani of the Robert Schuman Foundation, a Paris-based think tank, said the protests are major sign of discontent among liberal voters who feel shut out of the race. 

"This is how the leftists are expressing their frustration with the fact that they have no one to vote for in the second round," he said. 

Late Thursday, about 500 students — many young leftists among them — held a peaceful, anti-Le Pen sit-in at the imposing Pantheon landmark in Paris. 

"We have no choice. Even those who voted for the far-left have to vote for Chirac to block the far right," said student Arnaud Pujal, 23, who voted for Trotskyist candidate Arlette Laguiller of the extreme left. 

Severine Schrameck, a member of a student group that organized "dead day" said she doesn't remember a time when students mobilized so quickly or so passionately for a cause. 

"It has been a very long time since we had something like this," she said. "Students are very worried, and thus we call on all citizens to vote. We don't want the second round to be a presidential election so much as a referendum on the question of, 'Are you for or against the Republic." 

For the fifth day Thursday, tens of thousands of French of all ages, backgrounds and political stripes stormed the streets to denounce Le Pen. 

Between 150,000 and 250,000 young people marched Thursday against Le Pen's National Front party, including 15,000 in Nantes; 9,000 in Brest and Avignon; 7,000 in Lyon and between 1,500 and 5,500 in Vannes, Rouanne, Dijon, Montpellier, Saint-Nazaire, Toulouse, Rouen, Strasbourg and Aix-en Provence, French media reported.