Let's talk about something rationally for a moment. Just a moment.
Can you effectively maintain the interest and engagement of first, second and third graders of all combined levels in the same classroom? Can you manage to teach level-appropriate material to those students that will keep everyone learning and leave no one behind all at the same time? Can you do it in Korean? Can you do it in a language the students, for all intents and purposes, do not speak?
That is actually what you're asking me to do. And that's cool. I know how to work it out. But I just want you to know....
If you expect me to be able to do things that you probably couldn't, or would at the very least never even try to do, then it might be time to stop condescending toward foreign teachers. Given that I am one.