Why teach them in their own language?
In public schools:
We don’t teach English.
We don’t teach Math.
We don’t teach History.
We don’t teach Civics.
Actually, why have schools at all?
At least, why have schools populated by can’t major in real subjects NEA folks?
The vast majority of bilingual teachers I’ve ever seen have much poorer knowledge of the subject area, such as biology or math. They were hired primarily because of their bilingualism. And their English is usually heavily accented so that the students don’t really learn English at all. So you get poor instruction in the subject matter and poor instruction in English. A win-win for the stupid taxpayers who allow this.