There are fewer things more nerve-wracking to a CFI than waiting for a freshly soloed learner to return from a flight as night is falling. This is particularly true when the learner has not been trained for or endorsed for solo flight at night. You think your parents got upset when you broke curfew? This is worse.
My first exposure to this was at a school in Seattle. I was a freshly minted instructor assigned to an evening ground school, and when I walked to the CFI office, I found a coworker having a meltdown because one of his students had gotten caught out as night fell.
