Stop means Go
“STOP IT.” essentially means “GO FOR IT I DARE YOU.”
When we ask students to stop acting out by not offering any choice in the matter, then of course they’ll go right ahead and do it.
Take a kid I was looking after recently.
The more you said ‘stop that’, the more they’d ignore you and keep doing what you just said not to do. As soon as you’d look away, they’d sneak around and rebel.
“Stop it.” gives no options, it gives no reasoning behind why you’re saying it.
Instead try:
“I don’t like [insert misbehaviour], because [insert reasoning]. Could you please do [insert good behaviour]?”
Of course that won’t work all the time. Reasoning for younger children might blow over their heads, but at least they know there’s a reason WHY you’re asking them to stop.
A bonus tip is to have that reason prove how you CARE about them.
E.g “I don’t want you to do that because you’ll injure yourself, I care that you’re ok and safe.”