Walking through the gray prison corridors, the toddler shows no fear of the black-clad guards or the barred doors. Born in the Santa Martha Acatitla penitentiary in Mexico City, Said has been behind bars all 1.5 years of his life. His situation isn’t unique—Mexican law allows children to live with their mothers in prison until up to 6 years old in some areas, and there are more than 300 infants locked up across a country with the seventh highest inmate population in the world.

It’s a grim existence, but when Saskia Niño de Rivera leads Said and his mother to a small library she built inside the jail, everything changes. The toddler is taken away from the gray world of the penitentiary and is surrounded by bright colors, beanbags, children’s books and toys. It’s only ­temporary—later that night, he will return to eat among prisoners and sleep with his mother in her cell.

“This is where Mexico’s problem is,” says Niño de Rivera, the athletic and tireless 27-year-old director of Reinserta un Mexicano, or Reintegrate a Mexican, an NGO that aims to transform the nation’s jails. “Mexico has a huge security problem, and that is for the most part because we don’t have a penitentiary system that works.”

Niño de Rivera works to make a better space for the children caught in Mexico’s prisons, as far away as possible from other inmates, who are in for crimes including kidnapping, murder and drug trafficking. She is also campaigning to lower the permitted age children can be in the jail to 3 years old across the country, and eventually stop them being allowed there at all.

Ross McDonnell for TIME

The “children in prison” project is one of several arms of Reinserta, which has expanded rapidly since Niño de Rivera founded it in 2013. It also works with young offenders and female prisoners, and fights to get innocent people out of jail. Niño de Rivera doesn’t just do this to help the inmates but also because she believes it is the only way to stop the vicious circle of crime in Mexico. The children of convicts need to be given a better life or they will themselves turn into criminals.

Niño de Rivera has witnessed the devastation of Mexico’s crime epidemic firsthand. When she was 17, thugs kidnapped her uncle for ransom and held him for more than a month. She stayed with her cousins watching the painful negotiations until he was released. “That hostage situation defined what I do today with my life,” she says.

Reinserta tries to prevent the imprisoned infants from returning to jail as adults by educating both them and their mothers. “We have seen intense changes,” says Hazael Ruiz, the under secretary for the penitentiary system in Mexico City. “The children have shown improvement in their behavior, and the mothers have become better parents.”

Niño de Rivera also works to break the cycle by getting young offenders into school and helping them start their own businesses. Felipe entered a halfway house run by Reinserta after serving a three-year sentence for armed robbery. Now 19, he has a business selling dried fruit and a scholarship to study with a private high school. (He has also faced death threats from former criminal associates, so his last name was withheld for security.) He says Niño de Rivera and her team have saved his life. “If it wasn’t for them, I wouldn’t be here,” he says. “The world of crime has two paths: one to jail and one to death.”

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