...Indonesia’s linguistic legacy is increasingly under threat as growing numbers of wealthy and upper-middle-class families shun public schools where Indonesian remains the main language but English is often taught poorly. They are turning, instead, to private schools that focus on English and devote little time, if any, to Indonesian....

In 1928, nationalists seeking independence from Dutch rule chose Indonesian, a form of Malay, as the language of civic unity. While a small percentage of educated Indonesians spoke Dutch, Indonesian became the preferred language of intellectuals.

Each language had a social rank, said Arief Rachman, an education expert. “If you spoke Javanese, you were below,” he said, referring to the main language on the island of Java. “If you spoke Indonesian, you were a bit above. If you spoke Dutch, you were at the top.”

Leaders, especially Suharto, the general who ruled Indonesia until 1998, enforced teaching of Indonesian and curbed use of English....

With Indonesia’s democratization in the past decade, experts say, English became the new Dutch....