It's an idiom because (It's) pretty good; (it's) not as unpleasant as one may have originally thought.
It helps develop the theme because with the teacher being strict Kevin no longer tries to get answers from his father and listens to the teacher and Kevin learns from it.
<em>The Interesting Narrative of the Life of Olaudah Equiano </em>was the first autobigraphy of a slave. It was first published in 1789 and made an impact on Britain, as it made many of the people who read it to support the abolitionist cause.
Equiano converted to Christianity in 1759 and used its Golden Rule of "do unto others, as you have done to you" to reach the audience and try to change their approach towards slavery.
His Christian's beliefs were a fundamental part of his life, especially on his way to become a prominent anti-slavery figure and a writer.