Try to learn some specifics about the community and anticipate difficulties that may arise. There may be literacy issues and they may be unfamiliar with the concept of a structured course with progression and tests. There may be other issues which are less obvious- some indigenous languages don't use numbers or organise time in ways we can take for granted, so things which appear obvious to us become culture-specific. I haven't taught in South America, but I believe some indigenous languages don't count beyond three, which could quickly turn a lesson 'how many' into chaos, so getting to know the concepts behind their language(s) will help. Learning a language can be very entering very unfamiliar territory, so guide them into it gradually- give them the most basic navigation tools they will need and allow them to develop confidence.