Most schools do things like teach a multitude of languages and communication skills that would be useful for encoding harmful intent. Yet, most bullying happens using the native tongue and simplistic messaging. Rare is the student who is bullied via poetry and the five paragraph essay. Rarer yet is the student bullied via Morse code. I would be willing to bet that no child ever has been bullied in a classroom using secret Morse code. Mostly because Morse code cannot be tapped out. Contrary to the movies, you need to know when the tap ends to decode it, so knocking or tapping is not a reliable way to send a message.

Narrowing kids educational resources and knowledge in an attempt to stop bullying is a fools errand.

Who is spending weeks learning and practicing Morse, and also getting their friends to buy-in, just to bully people discreetly?

When I was in school, they'd just come up with agreed upon dog whistles and use them in front of you, directed at you. They'd usually be otherwise innocuous but packed with some alternative meaning only the in-group knew until they told you.

That's a lot less effort than learning an entire communication system.

Better prohibit kids from learning ASL and the manual alphabet, too! Or "foreign" languages.