You don't mention which chapter you are talking about, but I am going to assume you mean chapter 10, which is entitled "Miss Riley." Miss Riley is Homer's chemistry teacher in 11th grade. She is a very dedicated and inspiring teacher. Roy explains that she loves her subject, she is humorous, and she sticks to the point, not going off on tangents like some teachers. Roy also describes her as being an "inventive" teacher. She receives little money or equipment from the school district, but she is still able to make her classes exciting with what little she does have. She takes Homer under her wing, and she is the champion for "The Rocket Boys" at school. She defends them and helps them out, going to bat for them on many occasions, like trying to get the calculus class later in the novel.
Also in this chapter, Miss Riley tells Homer that she knows about a book on building rockets that she will try to procure for him. Later, she obtains the book and gives it to him saying:
"All I've done is give you a book," she said. "You have to have the courage to learn what's inside it."
If you are referring to a different chapter, please let me know.