Keep them playing. Most people who have gotten through the school system and still are artists and scientists would agree with this because that's what we do as adults. We have retained this playfulness and we tend to look at the world as a place in which to play. In a traditional society you don't need schools because kids see what adults do. For special things, there are initiation ceremonies that have to do with the mysteries of sex and so forth.
Kids are out hunting squirrels with toy bows and arrows.
On a small scale, they are imitating in a very serious way what the adults are doing with water buffalo. In the 20th century it's all form and no content. This is true with lots of things in the 20th century. The main objective of any educational system should be to try and get the largest possible number of children to grow up thinking better than their parents did. Science's way of representing knowledge is not as 'truths' to be believed dogmatically, but as 'best attempts' at mapping an interesting situation with accompanying criticism of what the roles of this map are and how it's expected to correspond and differ with what's actually out there.