More than 161,500 protesters gathered across the country to express frustration with school standards, according to reports. The demonstrations came after the government pledged last Friday to hire more teachers and address student concerns, though protesters said the measures fell short.
While many rallies were peaceful, some turned violent when masked protesters threw projectiles at police and lit fires in the streets. Authorities fired tear gas to control the crowds.
Thunberg appeared at a protest in the Parisian suburb of Saint-Denis, a working-class area where students said their school did not have adequate funding. She called for a better deal for the younger generation and expressed awe at the students' actions, saying the whole world is watching.
The protests, which began in September, have drawn growing international attention. Students are demanding more teachers, better school facilities and repairs to basic features such as bathrooms.
With national elections six months away, the protests have attracted political figures. Presidential candidate Jean-Luc Mélenchon of left-wing party La France Insoumise joined rallies to show support for younger voters.
However, Marine Le Pen of the National Rally, who leads in opinion polls, condemned the violence. "Those who vandalise our schools, and their parents when they are minors, must pay for the damage they cause," she said last week.
Thunberg's involvement has amplified calls for young people in other countries to demand social justice.