Culture makes teaching ESL difficult: there are a lot of things which need to be communicated, but they’re uncomfortable subjects. How do you deal with these things in a group setting?
The students in China are taught grammar; they’re taught to introduce themselves politely and to discuss their day. They’re not taught how to find a toilet.
Younger children are not likely to find themselves without parental assistance in an English-only situation, so there’s no need to go into extreme detail. Regardless, it’s a good idea to teach them common phrases such as “Could I please be excused” and “Where’s the washroom, please?” You could also cover common terms like toilet, washroom, restroom, lavatory and loo, and toilet paper. Younger kids really like the word flush. ( Here’s a page with wav files, in case you need one.) If you have a group that’s okay with it, you can introduce words like pee and poop, particularly in the context of pet care. As long as the terminology is age-appropriate, there won’t be a problem if they use the words around parents or teachers.
Older children – who are much more likely to be caught by themselves in sticky situations while on vacation or something – are more reluctant to discuss anything personal so it’s better to broach the subject while they’re younger. With older students, you’ll have to find delicate ways of introducing the terminology: at the beginning of winter, we usually discuss “being sick”, and include “upset stomach” along with “have a cold” and “have the flu”. Boys like to read James Herriot’s short story Cedric (about a dog with digestive gas) so they can learn the word “fart”.
Of course, the problem with (or good thing about, depending on your perspective) student-led learning is that you may find yourself discussing the topic even though you hadn’t planned to do so. I had one sweet little 8-year-old girl tell me about her new rabbit and the sh** it left all over the floor… so we had to go over “appropriate terminology” for rabbit droppings, and when it was okay to use the word sh**. I also had private classes with a teenaged girl who was going to the States for a year, and she skittered around the subject for about 5 minutes before I realised she needed to ask about feminine hygiene.
If you’re preparing slides, illustrated clip art goes over better than photos, or you can thieve funny photos from Google (I use this one , which the kids think is hilarious).