It's difficult to say anything without being branded a raciist. However, to be constructive, I suggest that an english test should be administered by an appropriate Embassy or Consular official before a visa is provided. That might provide sufficient motivation to excel.
My partner teaches, and has a never ending problem with kids from other places whose English is substandard and who don't really went to learn, moreover, they posess cultural imperatives to say "yes'" when the real answer should be "I don't understand a f&8*ing thing you just told me".
Thats what has been at the back of my mind about the NAS "recommended calls", God knows my voice procedure is not perfect, but at least I try. What worries me is the guy who is not sure what to say or how to say it, and therefore shuts up completely.
The poor CFI's have a lot on their plate.