I declare that, as an employee of the Government of the Hong Kong Special Administrative Region of the People’s Republic of China appointed on non-civil service terms, I will uphold the Basic Law of the Hong Kong Special Administrative Region of the People’s Republic of China, bear allegiance to the Hong Kong Special Administrative Region of the People’s Republic of China, be dedicated to my duties and be responsible to the Government of the Hong Kong Special Administrative Region.
Often when you teach a language to students, you won't know their language. I've taught classrooms in US where I have Arabic speakers, Chinese speakers, Turkish speakers, Spanish speakers etc. all in the same class. I don't speak most of those languages whatsoever and there aren't translators on hand. If students are above a basic level, this works fine. You can explain English language concepts to students even if they have a limited vocabulary. If they know no English at all its an issue, then they'll need to utilize more bilingual materials or have a bilingual teacher.
Same is true teaching abroad, but usually you're working with students who share a common language. Therefore schools usually have bilingual teachers from that country in addition to native speaking teachers. Worse schools/teachers might mostly just utilize a foreign face that doesn't do much besides speak natively accented English, better schools actually have foreign teachers who are certified to teach or have experience teaching.