I saw it about 15 years ago (on VHS), but don’t remember if it was current then or older.
The main character is a schoolboy and is new to the school where the movie is set. I think it’s a boarding school, and everybody wears a uniform.
It takes place in Britain, Australia, or New Zealand (everybody has accents but I don’t remember which one of those it was).
One of the teachers has her class practice enunciation by repeating the sentence “I would like a piece of cake.” When demonstrating for the class, the teacher exaggerates the vowel sounds. This is the only scene I remember.
Not much to go on, but if anybody can pull the proverbial rabbit out of the hat, I’ll be grateful and put you in my will.
Thanks.