I must have been about fourteen at the time. The headmaster (or high school principal) convened a regular daily assembly of the school. Small excitable children don't always stop talking fast enough for authority figures. This particular time it must have been too much for him, because he shouted:
Every time I open my mouth an idiot speaks.
There was no irony here, and he really had no idea what the joke was. I remember looking at all of the teachers to see their reaction. You could tell a lot about school politics from which people were openly laughing and which ones were staring at infinity, sucking in their cheeks.

This wasn't an isolated incident either. Another time at assembly he said:

Boys will NOT play with their balls in the covered area. Otherwise a member of staff will approach them.
I suppose the fact that this person was directing my education really ought to annoy me, but in truth I remember him rather fondly.