The cash from the milk accumulated, and Beatrice’s parents decided that they could now afford to send their daughter to school. She was much older than the other first graders, but she was so overjoyed that she studied diligently and rose to be the best student in the school.

Image Nicholas D. Kristof Credit... Fred R. Conrad/The New York Times

An American visiting the school was impressed and wrote a children’s book, “Beatrice’s Goat,” about how the gift of a goat had enabled a bright girl to go to school. The book was published in 2000 and became a children’s best seller  but there is now room for a more remarkable sequel.

Beatrice was such an outstanding student that she won a scholarship, not only to Uganda’s best girls’ high school, but also to a prep school in Massachusetts and then to Connecticut College. A group of 20 donors to Heifer International  coordinated by a retired staff member named Rosalee Sinn, who fell in love with Beatrice when she saw her at age 10  financed the girl’s living expenses.

A few years ago, Beatrice spoke at a Heifer event attended by Jeffrey Sachs, the economist. Mr. Sachs was impressed and devised what he jokingly called the “Beatrice Theorem” of development economics: small inputs can lead to large outcomes.

Granted, foreign assistance doesn’t always work and is much harder than it looks. “I won’t lie to you. Corruption is high in Uganda,” Beatrice acknowledges.

A crooked local official might have distributed the goats by demanding that girls sleep with him in exchange. Or Beatrice’s goat might have died or been stolen. Or unpasteurized milk might have sickened or killed Beatrice.

In short, millions of things could go wrong. But when there’s a good model in place, they often go right. That’s why villagers in western Uganda recently held a special Mass and a feast to celebrate the first local person to earn a college degree in America.