"don't make a child speak for an entire culture" I love this one. I have many students who are immigrants or they are the children of immigrants. Not everyones' experience is the same. In fact some are wildly different due to political or socieconomic factors. If information is offered by the student, that's a great invitation for discussion, but not everyone wants to be the poster child for (insert issue here).
Look out for culturally unique vocabulary. Once I had an Arabic speaking student point out that the English language has a lot of violent expressions and idioms in it. We made huge list: "kill two birds with one stone, crush it, blowin up," just to name a few. When we compared it to Arabic translations or equivalents, the expressions were still there but were softer. For example "swat two flies with one swat." We challenged the notions of extremism. It led to a thoughtful conversation about language across cultures.
