We had a contra group in Edinburgh for a few years that worked very well and did a few square dances. It was never very big, and no way would something that split the dancers into "levels" be viable - goes right against the grain of any kind of Scottish dance culture. Even the fairly regulated RSCDS will fit in anybody who can understand the instructions.

On the other hand, I could see a workshop getting enough takers if it aimed to teach a few basic square dances and how to call them.