We are in a drawing club that meets outside once a week.  The kids run and play and draw as they wish.  Yesterday, one mother pulled out watercolors and set to work sitting on her blanket.  Later, I looked over my shoulder and she was surrounded by 10 kids - including both of mine.  In another hour I was ready to leave.  I looked over my shoulder and those kids were all still there, heads bowed over paper, engaged, still, earnest, working.  They worked until they were ready to stop - I had long since been ready to go. They worked independently but together, without competition, grades, or thoughts of time.  Later, they called it fun.