At least 50 people were arrested in the Chilean capital Thursday amid clashes with police during a student demonstration over the quality and cost of higher education. The demo involving some 5,000 protesters also saw three policemen hurt, one of them seriously, in the hours-long clashes, police said. Authorities used water canons and tear gas against the demonstrators hurling stones and other missiles. The clashes erupted after police attempted to break up the protest, which authorities said had not be given official approval. Chilean students staged more than 40 street marches last year. Some of them marked the country's largest rallies in the past two decades, drawing more than 100,000 people. Several marches resulted in clashes with police. The students, backed by professors and labor unions, are demanding President Sebastian Pinera's conservative government to overhaul the education system to guarantee free, quality university-level education for all Chileans. The protests have been the biggest, and most sustained, since the end of the dictatorship of Augusto Pinochet more than two decades ago. Under Pinochet, state funding for public education was slashed, privatization encouraged and responsibility for public schools passed to municipalities. The result has been a highly segregated system in which those who can afford it attend private schools and those who can't are relegated to lower quality public schools.