In a school where most of the kids are British Asian (and have English as a second language), I've found it quite entertaining to see the Asian kids SPEAK ENGLISH LOUDER at the central European kids just acquiring the language.  SHOUTING AT FOREIGNERS is supposed to be a particularly Anglo vice, so I don't know whether it's innate to these children or whether it's something they've learned because they or their parents have been on the receiving end of it.

I've found that explaining (in French) that shouting doesn't help and then repeating myself LOUDER AND LOUDER generally gets the point across.