Final answer:
The passage's primary purpose is to persuade readers that movie rating systems are insufficient and that parents should use personal judgement to decide what their children watch, tailored to each child's maturity.
Step-by-step explanation:
The primary purpose of the passage is to persuade. The parent expresses dissatisfaction with the movie rating systems, explaining that such systems lack the nuances to understand individual children. Instead of relying on ratings alone, the parent advocates for personal judgement to determine the suitability of content for their children, arguing that direct experience and knowledge of one's children are essential for making informed decisions about media consumption. This persuasive argument outlines a subjective view on the effectiveness of media ratings and suggests that one-size-fits-all approaches do not account for individual maturity and sensitivity levels among different children.