Is bilingual education desirable in multilingual countries?

Many developing countries are populated by multiple ethnic groups who use their own language in daily life and in local business, but have to use a common language in national business and in communications with other groups. In these countries, how much weights should be placed on teaching a local ethnic language and teaching a common language is a critical issue. A similar conflict arises in low-income countries in general between teaching skills that are "practical" and directly useful in local jobs, and teaching academic skills that are important in modern sector jobs. This paper develops a model to examine these questions theoretically. It is shown that balanced education of the two languages/skills is critical for skill development of those with limited wealth for education. It is also found that the balanced education brings higher earnings net of educational expenditure, only when a country has favorable conditions (TFP is reasonably high, and education, in particular, common language education [academic education] is reasonably e¤ective) and only for those with adequate wealth. Common-language-only (academic-only) education maximizes net earnings of those with little wealth, and, when the country's conditions are not good, maximizes net earnings of all. This implies that there exists a trade-off between educational and economic outcomes for those with little wealth, and, when the conditions are not good, the trade-off exists for everyone without adequate wealth. Policy implications derived from the results too are discussed.