Defying police water canon and tear gas, tens of thousands of Chilean university and high school students marched through the streets of downtown Santiago to re-ignite calls for free quality education.
Student groups said as many as 80,000 students participated in the latest demonstration which was the first official protest of the year organised by the Chilean Student Confederation.
Police officials put the number closer to 48,000.
Students held seven months of demonstrations in 2011 protesting centre-right President Sebastian Pinera and criticising the higher education system students say is geared to generating a profit and not to educating the people.
As police tried to break up the crowd and students fired back with rocks and other projectiles, a band of demonstrators apparently separated from the group and set a government security building on fire.