I've been watching presentations of English teachers on iTaki and what I've noticed. Disclaimer: I would not want to offend someone but if I offend you or your friend I am really sorry! I watch USA series and thought that all americans pronounce R very sonorous, like a cat purrs. But all the teachers pronounce it in a different way. Bright "R" is common for New York teachers and not for others. Other american teachers pronounce "R" like Canadian or British people. But I have met a man with so huge accent on "R" that it looks like that "R" is everywhere and he is like a tomcat. It is very nice. There was teachers those are very good and take less price. But I was astonished that a teacher who stammers and starts one word then changes it to another asks the top prise. (Can I say a sentence after "that" in the present or it should be whole in the past?) And third type of teachers: who is doubtfulness. I doubt that they are native speakers...