> start blinking in morse code

In at least one famous incident, this skill proved very useful:

https://www.archives.gov/exhibits/eyewitness/html.php?sectio...

You'd have to know those existed. These children are quite young, and might not have heard of Morse code (and hand signing slows eating down nearly as much as speaking).

My class learned to sign letters in like 3rd grade. The usual suspects very blatantly signed, letter by letter, to each other across desk aisles and still got caught. We never did make it to words.