13-year-old credits earthquake drills with helping him escape collapsed school Citywide drills were held to mark the 32nd anniversary of a 1985 quake.

 -- A student of a Mexico City school that collapsed after a powerful earthquake hit the capital Tuesday told a local reporter that he escaped because of an earthquake drill held earlier in the day.

Search-and-rescue teams continue to frantically search for victims trapped under the rubble of the Enrique Rebsamen primary and secondary schools more than 24 hours after the earthquake struck. So far, the bodies of 21 children and four adults have been discovered at the site, said Mexico's Education Minister Aurelio Nuno. Eleven people have been rescued and three are still missing.

Rodrigo Heredia, 13, told a reporter for Televisa in Spanish that the escaped the building because school protocol took him and others down a set of safe stairs and out to a meeting point.

The first exit was blocked and the group had to find an alternative way out, Heredia said. In order to get to the safety of the street, they were forced to scale a collapsed wall.

The drill had been practiced earlier in the day, Heredia said. Earthquake drills were held all over the city Tuesday to commemorate the anniversary of the Michoacán earthquake in 1985, which killed thousands and caused catastrophic damage in Mexico City.

The earthquake alerts gave them little warning, said Heredia, who was still wearing his school uniform from the day before under his jacket.

The teen said it is very difficult" to know that his school has been destroyed. Two of his friends were injured in the disaster, but they are safe now, he added.

A 7.1 magnitude earthquake struck around 2:14 p.m. ET Tuesday near the town of Raboso in Puebla state, according to the United States Geological Survey. The earthquake came nearly two weeks after an 8.1 magnitude quake struck off the country's Pacific coast.

The school was one of the dozens of buildings that were leveled by the earthquake. Mexico City is built on a former lake bed with soil that amplifies the earthquake's seismic waves.

More than 200 people have died as a result of the quake.

ABC News' Matt Gutman and M.L. Nestel contributed to this report.