Final answer:
The minimum age for a staff person to be left alone with children is generally 18 years old, as per federal guidelines like the FLSA, and reflecting the age at which one is considered an adult in the United States.
Step-by-step explanation:
The minimum age of a staff person that can be left alone with children varies based on state and local regulations; however, if we look to federal guidelines such as those established by the Fair Labor Standards Act (FLSA), individuals must be at least 18 years old to perform hazardous work without supervision, which might apply to working alone with children. Furthermore, the definition of when a person becomes an adult is context-dependent. For example, in the United States, a person is legally considered an adult at 18 years old, but the definitions may vary in sociological or cultural contexts. While earlier labor laws, such as those of the 19th century, established a minimum working age of 9 and specified workday length for children ages 9-18, modern standards are much stricter regarding health, safety, and encouraging continued education.