That's about all I can remember.
The twist to the story is the mysterious sound the main character heard:
There is a room where nobody can enter, and in it is a wheel that is used to grind stuff into dust. Possibly for potions? The main character suspects they're grinding bones.
He ignores his misgivings and strives to be the number one pupil.
I think his mentor dies and when he finally becomes the top pupil he realises why.
The students turn on him and try to kill him so that they can grind his bones into dust! Or for whatever sinister reason.
Whether he escapes or not is blanked in my memory.