Under capitalism, childhood education is the means of providing a child with the knowledge they require to become an independent, self-sustaining, rational adult.
Writes Ayn Rand, on the purpose of education:
“The only purpose of education is to teach a student how to live his life—by developing his mind and equipping him to deal with reality. The training he needs is theoretical, i.e., conceptual. He has to be taught to think, to understand, to integrate, to prove. He has to be taught the essentials of the knowledge discovered in the past—and he has to be equipped to acquire further knowledge by his own effort.” 
 Ayn Rand “The Comprachicos,” Return of the Primitive: The Anti-Industrial Revolution