Clashes have erupted in the Chilean capital, Santiago, as thousands of students marched to press their demands for changes to the education system.
Masked protesters fought pitched battles in the city centre with police who fired water cannon and tear gas.
Students, who have been demonstrating for weeks, say the current system is under-funded and unequal.
President Sebastian Pinera has pledged extra funding, but students say this is not enough.
Interior Minister Rodrigo Hinzpeter said the violence showed that student leaders could not control their demonstrators.
The demonstration began peacefully with tens of thousands of students and teachers marching through Santiago and elsewhere in Chile.
But masked protesters then split off from the main crowd and began clashing with police.
Reports said masked demonstrators burnt cars and barricades, looting shops and throwing furniture at police.
Student leaders said 150,000 people marched in the capital’s sides streets after they were denied permission to demonstrate on the main avenue.
Officials estimated the crowd at about half that number.
«The government is not listening to us. We want a new education system in Chile and the government proposals do not address what we want,» Miguel, a student at the University of Santiago, told AFP.
Demonstrations also took place in other main cities, including Valparaiso and Concepcion.
Deputy Interior Minister Rodrigo Ubilla said at least 273 protesters had been arrested nationwide, and 23 police officers had been injured in Santiago.
President Pinera has promised additional funds, but students say this will not be enough to repair a system that is both under-funded and unequal.
Last week, the government put forward a package of 21 reforms, including an offer to increase funding, improve teacher training, increase university scholarships and help resolve unpaid student loan debts.
But students rejected the plan, saying it failed to meet a key demand that private universities invest their income in educational improvements.
The nationwide stoppage is the latest protests by students who have taken over schools, staged kissing marathons and marched through towns.
The education protests come as President Pinera, in office since March last year, has seen his approval ratings drop to under 30%.