Twoway immersion (TWI) programs are a distinctive form of dual language education in which native English speakers and speakers of another language (usually Spanish) are integrated for academic content instruction through both English and the partner language. The goals of TWI programs include the development of bilingualism, biliteracy, and crosscultural competence in addition to gradelevel performance, and a growing body of research indicates that the model is successful in helping students to attain thes goals. At the same time, however, the extent to which students achieve these outcomes varies across schools, with many practitioners unsure about the approaches that are likely to yield the best outcomes.