If you’re teaching English writing skills, or looking for plenary ideas in any subject, then take a look at Doug Lemov’s excellent summary of an idea in Judith Hochman’s Teaching Basic Writing Skills.
As a teaser, here’s an example of but, because, so in action. You simply take a key idea from your lesson and then ask the pupils to extend it in three different ways:
Eva killed herself … BUT … many people are to blame for her death.
Eva killed herself … BECAUSE … she had fallen victim to an unpleasant chain of events.
Eva killed herself … SO … that she wouldn’t have to suffer any longer.
As a plenary activity, this would work with any subject, and it might well lead to some interesting revelations about the pupils’ thinking. If this idea sounds interesting, you might also want to check out this popular article on exit tickets.