
Sister Mary Killeen, right, has been working in the slums of Nairobi, Kenya, for nearly 40 years. On Friday, she'll be addressing Pope Francis, who is on his first visit to the continent.

Killeen arrived from Ireland in 1976. In her early days, she said, close to half of Kenyan children were out of school -- and in parts of the city street children would sometimes steal people's clothes. "One day a group of these children approached me," Killeen said. But rather than steal from her as she anticipated, they asked her if she could help get their siblings into school. "They said, 'We're already thieves, but we don't want our siblings to have the same life that we had.' "

Since then, Killeen has developed dozens of educational programs and schools. She estimates she's assisted in the education of 300,000 children over the years.

"I can't walk any part of the city without meeting a past pupil," Killeen said. "Driving a car, in an office, as a manager somewhere, on the TV -- I turn on the TV and I see a past pupil from Nakuru giving out the news. It's very, very fulfilling work."

Most schools border poor communities. Killeen says land issues are a constant battle and school land is often encroached upon by developers. "The minute corruption goes up, poverty increases," she said. "Among the poor, you see an immediate effect."

Killeen helped found Songa Mbele, a school that cares for kids with disabilities. The mother of Zain Modeitsi, seen here, used to have to leave him at home alone in order to work.

Killeen assists in a physical therapy session for Zain, a 10-year-old who has severe cerebral palsy. "I've seen children walking who couldn't walk," Killeen said. "I've seen the deaf get help, and a little dumb child here who hasn't spoken yet but with help hopefully the child will speak. So it's like the gospel. You see the lame walk, the blind see, the dumb speak. So it's really wonderful to be part of that and to enable it. But we aren't doing as much as we should. It's a drop in the ocean."

"Religions, I'm not all that fond of them," Killeen said. "Religion is a way to help you reach love, understanding. You can call that God if you want. I'm not for piety, I'm for religion in action."