LILLE, France—Growing up in northern France, Aurélie Chancelet had never had classes canceled for a snow day or a heat wave.

Monday afternoon, however, a crowd of demonstrators outside her university sent Chancelet and other students home early, marking another day of protests in France over proposed changes to hiring laws.

Several hundred demonstrators assembled in the streets outside the Catholic University of Lille, brandishing signs, stickers and slogans offering a mix of support and opposition for the proposed reforms, known as the First Employment Contract, or CPE.

Under the CPE, employers would be able to terminate job contracts for workers under the age of 26 without having to provide an explanation.

Supporters say the reforms will encourage employers to hire young workers and improve an employment situation in which one in five people between the ages of 18 and 25 is unemployed.

Two demonstrators, wearing stickers that read "Yes to the CPE," said a more flexible contract "only makes sense" for an employee's first experience in a full-time job.

But opponents say the changes will rob young people of job security and turn them into disposable workers.

One protester wearing a caricatured mask of a greedy businessman held a sign that described the reforms as "Gains for bosses, power for me, exclusion for you." Another sign read "Thief!" alongside a picture of Prime Minister Dominique de Villepin, an outspoken supporter of the CPE.

One anti-CPE demonstrator said she had originally come to the Catholic University of Lille for a planned visit from Minister of Finance Thierry Breton, who was scheduled to speak at 5 p.m., but joined the protest instead when the building closed for security reasons as crowds of protesters began to gather.

The CPE "gives too much power to employers," she said. "It's an attack on students."

Élodie Marc, a student at the Catholic University, said she was arriving for her afternoon classes around 3 p.m. when groups of demonstrators began gathering in the street outside the university.

She said a number of the university's students lined up in front of the building to discourage protesters from vandalism by students from other schools.

"We didn't know if they would be violent," she said.

A handful of police vehicles and a few dozen officers were on hand to monitor the crowd. The demonstrations were largely peaceful, although officers moved the pro- and anti-CPE crowds to opposite sides of the street and stationed themselves in between after the two sides, which had been mingling in the middle of the road, exchanged a few volleys of thrown bottles, fruit and trash.

Both Marc and Chancelet said they joined briefly in the demonstration to voice their opposition to the student strikes in protest of the CPE that have disrupted classes at a roughly half of France's public universities, sometimes barring non-strikers from attending as well.

Students "have a right to demonstrate if they don't support the CPE," said Marc, "The thing is, they prevent other students from going to school."

The reforms proposed by the CPE have been hotly debated since Villepin unveiled them in mid-January. Monday's demonstrations came on the heels of larger weekend gatherings, in which organizers and local authorities estimated anywhere from 10,000 to 30,000 people participated in Lille, along with several hundred thousand in Paris.

One CPE supporter said while he does not expect the reforms to pass in the face of such widespread opposition, "something needs to change."

"Things can't stay like this," he said.