A little boy liked chasing little girls on the playground. They put a stop to that with 1 word.

It might seem small, but teaching kids from a young age the importance of stopping when someone says "stop" means they're more likely to respect each others' boundaries as adults too.

The whole conversation actually sounded like this, but I couldn't get it into 140 characters:

ME: "What did you do at school today?"

HIM: "Play."

ME: "With who?"

HIM: "There are some girls I like. I used to to chase them, but they told me they did not like being chased. So I stopped. Now we all play what we all want to play."

ME: "That's cool little man. It's totally cool."