What does big ma force Cassie to do in Roll of Thunder Hear My Cry?

In "Roll of Thunder, Hear My Cry," Big Ma forces Cassie to apologize to Mr. Barnett, the white store owner, after an incident where Cassie feels wronged by his disrespectful treatment. This moment highlights the racial tensions and injustices of the time, as Big Ma believes that maintaining peace and avoiding trouble is essential for their family's safety. Cassie's struggle with this demand illustrates her growing awareness of the societal injustices around her.