"Children also helped build Nauvoo. If they were old enough, they helped take care of the animals and the farms, gathered wood and berries, and helped make cider, soap, and candles. They also went to school. One group of young boys helped in a unique way. Many criminals came to Nauvoo, and the Saints did not want these people in their city but did not want to use violent means to get rid of them. A group of boys was organized into a “whistling and whittling brigade.” Whenever the boys saw a suspicious stranger on the street, they would surround him and walk along with him. They would not speak, but would just whistle and whittle as they followed the stranger wherever he went. It would be annoying and frustrating to the stranger, but he could not fight all the boys at once, so he would soon leave town."
Lesson 33 - Group of boys has a whistling and whittling brigade to help watch for bad people.
The lesson uses the words "young boys" and "children". The reality is that the brigade were older teens and not children. The impression the article gives is of primary children, but in reality they were full grown young men. Think of a high school varsity football team following you around with bowie knives.