That's three demerits for being late and three more for the fish story.
4 seconds sound clip from the The Sword in the Stone (1963) movie soundboard.
You can hear this line at 00:37:49.209 in the Blu-ray version of the movie.
Quote context
[...]
- Pin feathers and gully fluff.
- He was a monster. The biggest fish I ever saw.
- And, boy, that's the biggest fish story I ever heard.
- That's three demerits for being late and three more for the fish story.
- I told you the Wart was loony.
- He's either out of his head or... there's something mighty fishy going on around here.
[...]