A few years ago I heard a story on the radio about a kindergarten teacher who was honored for creating a bully-free environment, and one of the tools she used was ‘if someone wants to play, you can’t say no’.
Personally I was a little steamed, because we’d been saying that – and phrased in the positive way, no less – and I never saw a dime! Just kidding. Really, this will help SO much. Preschoolers are at an awkward stage – it’s the time when they learn that just because Friend A is playing with Friend B, they haven’t stopped being your friend. Many of them won’t understand that before they leave your class, but this is one tool that helps them interact.