Answer: neither
Explanation: a child is born with no emotion until later stages on depending on genetics there can be a higher chance of being bipolar or having mental issues but a child is born with a blank sheet ready to be filled
Which words best signal that "muchachitos mal educados" has a negative connotation?
The answer is raised their voices because 'to raise one's voice' means to speak in a loud angry way showing negative emotions.
I would say it is plural.