Image provided by Mexico's Presidency shows Mexican President Enrique Pena Nieto(C) posing for photos during a celebration of the Teachers' Day at the Official Residence of Los Pinos in Mexico City, capital of Mexico, on May 15, 2013. (Xinhua/Mexico's Presidency)

Image provided by Mexico's Presidency shows Mexican President Enrique Pena Nieto (R2) attending an event held to celebrate the Teachers' Day at the Official Residence of Los Pinos in Mexico City, capital of Mexico, on May 15, 2013. (Xinhua/Mexico's Presidency)

Image provided by Mexico's Presidency shows Mexican President Enrique Pena Nieto(R) taking photos during a celebration of the Teachers' Day at the Official Residence of Los Pinos in Mexico City, capital of Mexico, on May 15, 2013. (Xinhua/Mexico's Presidency)

Image provided by Mexico's Presidency shows Mexican President Enrique Pena Nieto (L) posing for photos during a celebration of the Teachers' Day at the Official Residence of Los Pinos in Mexico City, capital of Mexico, on May 15, 2013. (Xinhua/Mexico's Presidency)