No doubt, there are bilingual programs that do not work, whether it is because kids do not learn English or do not learn it fast enough. But the same can be said for mathematics, history and even English for native speakers. Everyone is familiar with the abysmal state of public schools in inner cities, which produce graduates who are monolingual native speakers of English, yet cannot string together a few sentences into a coherent paragraph. The same way schools shouldn't stop teaching history, they shouldn't stop bilingual ed. Teaching history is a good thing.
Bilingual classes are a good thing.
They just need to be done right. The primary goal of bilingual education should be, of course, to teach English to immigrant children. But it should not stop there. There also needs to be emphasis on maintaining a student's native language. Making a quick transition to English the sole goal of bilingual education is a waste of a student's native tongue.