Re: Back again, and let's first dispense with this nonsense...
The aim is simply for them to go away knowing more than they started (or at least have fewer misconceptions!) and for them to feel pleasure at having learned something complex about the Universe. It is not important for them to be able to pass an exam on it later.
Thanks cavediver. It works for me. I think that there are a large number of us who read through these threads without always feeling the need to post very regularly. I still remember you mentioning a few years back that this world is, metaphorically speaking, a projection. That in particular was really helpful.