How does an immersion school of English work?

Well, I think ideally that's what an immersion school ought to aim at, provided you can find staff sufficiently fluent in the target language. Most larger Canadian school boards run either French-immersion or English-immersion schools, and in this setting it's generally not too difficult to find support staff knowledgeable in the second language. I suspect that an English-immersion school in Brazil might have to adapt itself as best it can to the local circumstances.

Henry, thank you for commenting on my post. From what you've just told me, I suspect running a total-English-immersion school in Brazil seems next to impossible as hiring support staff knowledgeable in the target language would prove difficult. At least in Brazil, bilingual support personnel would probably ask for higher salaries, whereas total-English-immersion schools would rather hire non-English-speaking cheap labor hand, in which case they'd fail to attain the "total-immersion-English" status.

In a likely scenario we have the American School where maybe (some of) the clerical/secretarial staff speaks some English. I would not expect its maintenance staff to speak English, though. Nor would Norwood.