We’ve been discussing the benefits of dual-language (i.e., two-way bilingual) programs and late-exit bilingual education programs. But… here’s some recent research from Johns Hopkins University that finds no significant differences between transitional bilingual education and structured English immersion. For a quick preview of the research see this Learning the Language blog post.
Note that the research doesn’t review dual-language models. Nonetheless, a shift from a focus on the language of instruction to appropriate pedagogy seems warranted.
Literacy and the Bilingual/Bicultural Child 