Rocks fly in Mexico over a recently reformed education system.<br/> <br />The reform seeks competency exams, merit-based promotions and seeks to tame a powerful teachers' union blamed by many for hurting Latin America's second-strongest economy.<br/> <br />Teachers fear they could lose their jobs if they don't pass periodical, mandatory tests.<br/> <br />Parents -- some stepping in to replace striking teachers -- stood atop a school rooftop to try to defend it from being overtaken by protesting teachers.<br/> <br />Despite injuries sustained by protesters, police said they were able to maintain order.<br/> <br />(SOUNDBITE) (Spanish) OAXACA MINISTER OF PUBLIC SAFETY, MARCO TULIO LOPEZ, SAYING:<br/> <br />"The police at all times tried to keep the order inviting both parties in conflict to calm their violent attitude. I personally was here on this corner talking to people but there was not reason or capacity for dialogue."<br/> <br />Mexico's record on student achievement is one of the worst among countries by comparison
