Teachers in Mexico went on a riot on Wednesday. They are angry at changes to their jobs made by the government. Hundreds of angry teachers attacked the offices of political parties in Mexico's south-western Guerrero state. They broke windows, set fire to offices and sprayed graffiti on the walls. Thousands more rioters who are angry with the government joined the teachers in the streets. The state governor sent hundreds of police officers to guard the local government building. The police could not stop the violence, so mayor Mario Moreno asked for government support to control the situation. He told a local TV news station: "We do not have the ability to face a mob of 4,000 or 5,000 people."

The teachers are angry at changes that would take power away from their unions. Mexico's government wants more control over the quality of teachers and who becomes a teacher. Teaching unions currently assess the quality of education in schools. The government wants to do this instead, to make sure all schools have similar standards. They want teachers to pass tests to get jobs or get promoted. The government also wants to end the policy of buying and selling teaching jobs. Some teachers in Mexico give their position to a relative when they retire or quit. The biggest teaching unions are worried that many teachers will lose their jobs. They also fear that the government wants to control every school.