"I personally feel that more offensive still is the implication that the 'darkies' distorted the Bible stories and made fun of them. The inference was that their church was ridiculous and unworthy of respect."

The only place I have ever heard this song sung was at a Boy Scouts campfire singsong and the title was Darkies Sunday School. The chorus if I remember correctly went:

Young folks, old folks, everybody come
Join the darkies Sunday school
Bring your sticks of chewing gum
And squat upon the floor
And we'll tell you Bible stories
That you've never heard before

The bible stories contained in the verses were humorous and bawdy and certainly not the sort of thing you would hear in any Presbyterian Church in Scotland - far from making fun of "them" and disrespecting "their" church (Whatever that might mean - an Anglican Church, is an Anglican Church, is an Anglican Church irrespective of who walks through it's doors - but nobody can prevent people taking offence if that is what they deliberately set out to do) it is obviously sung from the perspective of a member of this Sunday School ("and WE'LL tell you) and makes the point that attendance is fun, informal and a thoroughly enjoyable experience, which Sunday School in the Presbyterian Church of Scotland most definitely was not in my young days. So if anything we sang the song to have a dig at "our" church (Note: Boy Scout Troops were all affiliated to specific Churches in Scotland when I was growing up - hence the connection).