Our textbooks are written in England. Usually that’s perfectly alright. Usually I find it rather charming. When teaching ESL, however, the differences which would ordinarily not have been an issue, such as Z being said “zed,” an eraser being a “rubber,” pants as “trousers,” “my mum is mad about footballing,” or the constructions of have: Sally has got a fish. What have Dave and Arleen got?” There’s nothing wrong with any of those, of course (as much as American youth might snicker at being told that Henry has got a rubber), until one tries insisting upon them, so that “I have a fish” is wrong, because it lacks got. It’s also uncomfortable teaching them as standard, since they sound (to me, because I’m American) like an acceptable but non-standard way to say something — certainly not as something to be memorized and insisted upon — especially the slightly quirky cliches taught (and memorized exactly) in the high school classes.