Final answer:
The societal norm reflected in the excerpt from Black Boy is the expectation of women to be submissive to men.
Step-by-step explanation:
The societal norm of the early twentieth century reflected in the excerpt from Black Boy is the expectation of women to be submissive to men, particularly within a marriage. The father's jaunty and smiling attitude despite the mother's distress shows the unequal power dynamic between men and women during this time. The mother's weeping and complaints about the unfairness of the judge accepting the father's word highlights the lack of agency and control that women had in their own lives and in the legal system.