Unfortunately, the boy was working on a different set of worries. He knew that whatever he wrote would be unflattering to the principal, and he was concerned he'd get into trouble over that.
I agree, though, that the school should have absolutely NO ability to interfere with the test taking; how else could the public be assured that the school is not giving answers or something else to increase the kids' averages to make the school look good?
Ummm,... I have news for you... Even when I was in school, the proctors would go by, look at my paper and make comments like: "Make sure you're answering the right question.", "Don't forget to check your math.", or just "Hmmm..." You knew.