If a student has learned AE pronunciation and spelling, then it's a bit tough on the student to say they cannot use it. I'd say that the major varieties of English are all acceptable. It's hard to say where this will take us- I have seen some argue that the language will eventually break up the way Latin did, while others say that the opposite is likely to occur and that the differences will be eroded. I think that at the fringes, some break up may occur, but I think the overall driving force will be to homogenise things, so national and regional variations are likely to become less marked.
- For Teachers