Student protesters clash with riot police officers during a rally in which demonstrators demanded that the government make changes to the public state education system, in Santiago April 11, 2013. Chilean students and their supporters took back to the streets in a massive demonstration in demands of free and quality education for all. Thousands of people, led by both secondary and university student organizations, marched through downtown streets in the capital city as they continue to demand an educational overhaul in the latest student demonstration since the movement began in 2011. REUTERS/Ivan Alvarado (CHILE - Tags: POLITICS EDUCATION CIVIL UNREST)