But is it?
Perhaps it is schooling that is the experiment- the gamble we take when we throw kids into institutionalized schooling.
After all, institutionalized schooling is a relatively new idea.. It's only 160 years old or so.
I would prefer to say unschooling adventure-rather than experiment. We can be experimenting with unschooling, We can experiment when we unschool- that is we can pursue interests and experiment with these interests.
But the act of unschooling is not an experiment. We are not conducting a controlled test. There are no controlled conditions. That would be schooling.
Here's a neat quote from a famous composer, Edvard Grieg:
He preferred the dream world to the real one. At the Bergen school he was regarded as both lazy and stupid. He devised all kinds of ingenious methods for being sent home from school, or for coming to school late. He hated his studies and resented being a continual object of ridicule for his teachers. "At that time," Grieg later recalled in an autobiographical sketch, "the school seemed to me nothing but an unmitigated nuisance, I could not understand in what respect all the torment connected with it were to a child's advantage. Even today I have not the least doubt that the school developed only what was bad in me and left the good untouched."
p315 -Milton Cross 'Encyclopedia of the Great Composers and Their Music (Doubleday 1962)

