Why did Phyllisia wait so long before answering the teacher's question?

Phyllisia's very much an outsider. As the daughter of West Indian immigrants, she feels somewhat alienated from the rest of society. And her outsider status follows her to school, where, like a lot of children who stand out from the crowd, she becomes a prime target for bullying. As well as her unusual background and exotic accent, Phyllisia stands out for being quite ugly, and that's always a handicap at any school. Furthermore, she's also very intelligent and knows all the answers to the teacher's questions. This makes her even more hated by the other girls in class, who resent her for being "teacher's pet."
But Phyllisia doesn't want to stand out any more than she already does. She doesn't want to make life any harder for herself. That's why she doesn't raise her hand in the air and volunteer to answer the teacher's questions; she only answers if she's specifically asked. So when Miss Lass asks the class which continent Egypt is located in, Phyllisia doesn't say a word until the teacher calls her by name, even though she knows the answer.