‘You can’t say you can’t play’ was a ground rule at The Classroom on Carpenter Lane, inspired by the teaching of Vivian Gussin Paley.
MacArther Genius Grant recipient Vivian Gussin Paley talked about the experiment she conducted in her Chicago kindergarten classroom on an episode of This American Life called The Cruelty of Children: http://www.thisamericanlife.org/radio-archives/episode/27/the-cruelty-of-children?act=3.
Vivian Gussin Paley wrote an important book called You can’t say You can’t play. (http://www.hup.harvard.edu/catalog.php?isbn=9780674965904)
Watch Vivian Gussin Paley talk about children’s play at a conference at the 92nd Street Y in New York City in 2008: https://youtu.be/wWxYRkmHNXM