DEHRA DUN, India -- At the Doon School, near the foothills of the Himalayas, life is spartan. The 500 boys enrolled here bathe together in communal showers. In winter, they pore over textbooks in rooms with no heat. Cellphones are forbidden and parental visits are kept to a minimum. For 71 years, Doon has supplied India with business leaders and well-known writers such as Vikram Seth. Even Rajiv Gandhi, the late prime minister, suffered the school's famously bad food. Now Doon is taking its uniformed students in a new direction: up the U.S. corporate ladder. The head of Citigroup Inc.'s...