Violence has broken out on the streets of Santiago, with riot police clashing with tens of thousands of student protesters seeking to put pressure on President Michelle Bachelet to reform Chile's education system.
Police used tear gas and water cannon against the protesters on Wednesday as the demonstration in the capital turned violent.
Students responded by throwing objects at the officers, with a number of arrests reported.
Officials say the protesters also destroyed street signs and bus stops.
There was no immediate word on injuries or how many people were detained by police.
Organisers said there were 80,000 protesters involved in the march, but police estimated the crowd at 20,000.
This is the second student march since Bachelet took power on the promise to provide better and free education, paid for by tax reforms that are passing through congress.
Bachelet's predecessor Sebastian Pinera was blighted by dozens of angry and sometimes violent protests by students demanding an overhaul to the privatised education system established under former military leader Augusto Pinochet.