I thought kids figured out social skills on their own. Then my son had a toy snatched and just stood there crying. He didn't know what to do because I'd never taught him.
Kids need scripts: "Can I have a turn when you're done?" for sharing. "Stop, please. I don't like that." for boundaries. "Do you want to play with me?" for initiating play. Walk away if someone is mean. Tell the teacher if someone gets hurt.
Social skills aren't magic β they're lessons. And someone has to teach them.