Police used water cannons and tear gas to break up a march by thousands of Chilean students on Thursday. It was the first protest this year by student groups whose demonstrations demanding education reform paralyzed major cities in 2011. Police said about 50 protesters were detained in Thursday's march on Santiago's main avenue, which drew roughly 2,000 participants. Organizers said 5,000 to 7,000 high school students took part along with some university students. The crisis over education reform in Chile remains unresolved despite seven months of mass demonstrations last year by students, teachers and families.