Miss Trunchbull kept the school late because this boy ate cake.
3 seconds sound clip from the Matilda (1996) movie soundboard.
You can hear this line at 00:43:42.228 in the Blu-ray version of the movie.
Quote context
[...]
- Shut up! The entire assembly will stay five hours after school and copy from the dictionary.
- Any children who object will go straight into the choky together!
- Miss Trunchbull kept the school late because this boy ate cake.
- That's the biggest lie I ever heard.
- I don't think it's fair, bumpkins.
- What?
- You get all this stuff from catalogs, and I don't get anything.
- It's not catalogs, it's car parts, sweetness. It's business.
[...]