There is not much difference between American pronunciation and British pronunciation. Teachers don't necessarily teach standards. You can learn the phonetic symbols first, and then search for the phonetic symbols of this word, so that you won't mispronounce it. Some senior teachers don't care much about spoken English. After all, British English pronunciation is not very accurate (from the new concept of adult version). If it doesn't work, you can find some professional training institutions. If the teachers there master spoken English and grammar, the impact will not be too great.