Why was Cassie disappointed in Strawberry?

Cassie received several big disappointments when she first
visited the town of Strawberry in the novel Roll of Thunder, Hear My
Cry. Living in a very rural area, Cassie was expecting great things upon her
first visit to Strawberry. But when she first arrived, she found the town nothing
special: It's highlights were one paved road and a street light. When her grandmother
was forced to locate their goods at the rear of the market, she later found that the
choice spots were reserved for white people. After disobeying her grandmother and
wandering away to shop, Cassie became angry when the shop owner waited on other white
customers instead of her. When she objected, the shop owner called her a "nigger." It
was not a happy day for Cassie, but it was a new if disappointing learning
experience.