When children already know something about dinosaurs, a lesson on the subject will make more sense when instruction shifts to English. The same principle applies when it comes to acquiring literacy. If we learn to read by reading, it will be much easier to learn to read in a language we already understand. Once you can read, you can read. The ability to read transfers across languages.
Social communication skills a.k.a.
English should not be confused with academic English, the cognitively demanding language that children need to succeed in school. Research on the effectiveness of bilingual education remains in dispute, because program evaluation studies featuring appropriate comparison groups and random assignment of subjects or controls for pre-existing differences are extremely difficult to design. Moreover, there is considerable variation among the pedagogies, schools, students, and communities being compared. This conclusion widely circulated by the so-called READ Institute has been rejected by the NRC study directors. Other critics continue to deny that such empirical support exists.