kcab, I don't think 'Tools of the Mind' seems new either. It sounds like what moms & dads & children have done forever. Little children mimic their parents. Little girls played with dollbabies; feeding, rocking, & changing them, just like mommy. They prepared food for their dolls and made clothing for them. Little boys wore their daddy's hats & boots; tagged along to the shop or on the farm, watching & trying to do what daddy did. The favorite toys of boys have been things to build with(or tear down!), farm animals, etc.
When you think about it, throwing a bunch of 4 & 5 year olds together with very little adult modeling seems very counter intuitive to teaching & training them to become adults. It sounds like the perfect environment to encourage wild, out of control behavior!
Therapists know the value of play therapy for children, it's about time our educational leaders understand it.