Facts
The school is offering art classes to all of its students.
Opinions
I love the sound of the singing birds outside of my window.
The Mona Lisa is the most beautiful of all paintings.
Math is a much more difficult subject than English.
Explanation
A fact is something that is true. An opinion is something that someone might think. Another person may think differently.
"The school is offering art classes to all of its students." is a true fact. It's not actually true, but it does not include <em>one's </em>thoughts.
"I love the sound of the singing birds outside of my window.
" is an opinion. Someone else might not love the sound of the singing birds outside of their window.
"The Mona Lisa is the most beautiful of all paintings.
" is also an opinion because someone else could believe different. Someone might think Starry Night is the most beautiful out of all paintings.
"Math is a much more difficult subject than English." is also an opinion. Another person might think English is harder than Math.
Answer. It emphasizes the boys' desire to follow rules.
The writer makes this clear when he says that even when the parents were not around to discipline his actions, Maurice still felt the guilt or the 'unease of wrongdoing'. Even though that he was thinking about an excuse, he was not feeling good about wrongdoing.