"Not all voice teachers are hostile to folk singing, Jim."
All the ones I have met, including those I have disussed folk music with, have fought their corner on behalf of their own
particular tastes in music - not to say that there aren't other things to be learned from them, but not sure that they can't be got elsewhere, thus avoiding the risk of being pressurised into singing to somebody else's tune.
Don't really want to get into an argument on this - would rather discuss the nuts and bolts of learning to sing.
One thing I want to add to my original posting.
It has been my experience that, physical defects aside, anybody can sing as long as they are prepared to put in the work - the more work, the better singer.
Jim Carroll