It's not real, the ceiling. It's just bewitched to look like the night sky.
7 seconds sound clip from the Harry Potter and the Sorcerer's Stone movie soundboard.
You can hear this line at 00:43:44 in the Blu-ray version of the movie.
Quote context
[...]
- We'll soon find out that some wizarding families are better than others, Potter.
- You don't want to go making friends with the wrong sort.
- I think I can tell the wrong sort for myself, thanks.
- We're ready for you now. Follow me.
- It's not real, the ceiling. It's just bewitched to look like the night sky.
- I read about it in Hogwarts: A History.
- All right, will you wait along here, please?
- Now, before we begin... Professor Dumbledore would like to say a few words.
- I have a few start-of-term notices I wish to announce.
- The first years, please note... that the Dark Forest is strictly forbidden to all students.
[...]