Laura,
were they amazed at how far their shadows had moved?
We often don’t think that the Sun moves that quickly, since it takes a whole daytime to go from the east to the west, but in the time it takes to draw two people’s shadows, the first person can’t fit back into their own shadow!
We did this in a summer course a few years ago, and it was remarkable to see the teachers who hadn’t tried this before react to their changed shadows.