That could even include a one-year immersion experience in English. But the key is to have a variety of viable options open to parents and students. The Emperor Has No Clothes. When I look at the empirical research on the subject, it shows that bilingual education is a little bit worse than the regular classroom and a little bit worse than a structured-immersion classroom, which is what the Unz initiative proposes. If you limit them to one year, then the danger of this happening is minimal.
Research shows that kids get stuck in structured-immersion programs, too.
The harm of being in a self-contained classroom consisting just of LEP kids would seem to be less if they're being taught in English than if they are being taught in their native tongue. Except that you can imagine how in U.S. schools, where newcomers arrive every day of the year, including the last, that these kids could get slowed down by the newcomers if they are there for more than a year. Although there's no research suggesting that one year is sufficient, it's common sense. Remember, most immigrant children go immediately into a regular classroom and they do better than those in bilingual education. Of course there needs to be more good research.