Do children really learn while they play?

It never fails when I give tours of my preschool to new families.  Someone always asks, "So, all they do is play?" or "My child plays at home, do I need to send him to preschool just to play?"

My answer is always some variation of, "YES!  Your children need to play and play and play.  They need to role play and play in the blocks.  They need to paint, draw, build, explore, observe, discover, and get messy.  They need to negotiate with their peers, take turns, make rules, and plan out how they are going to play.  Young children need lots of opportunities to play."

Play is so important to optimal child development that it has been recognized by the United Nations High Commission for Human Rights as a right of every child.

Classroom play is different from play at home in a number of ways.  First, of course, is that the children need the opportunity to interact and learn from their peers.  Also, the toys and centers that we plan for our preschoolers are "intentional," meaning that as teachers we have planned for the play in such a way that the children will be challenged to take on new roles, try new props, and think!

I always share this poem with my families at the beginning of the school year:

Unfortunately, it feels like society (teachers? school systems? parents?) places too much emphasis on getting young children ready for kindergarten.  As preschool teachers, we want our students to be ready for kindergarten academically, but we also realize that a child's job is to PLAY!  It is the way their young brains develop and grow.

So, what's your opinion?  Can preschool-aged children learn while playing, or do they need academic preparation to be ready for "real" school?  Is there a balance?