Tyler Cowen - Against Kindergarten?
It is a nice article, but in most cultures, disciplining a child is considered to be a mother's job, as a result, families with strong "family values" where the mother of the household is able to discipline their child in early years would allow these children to be more successful. Therefore, it is no surprise that keeping these children longer at home would improve their performance. Like all mother-child relation, the stronger the motherly love, the stronger the child will perform academically. Another aspect of the mother-child bond is co-sleeping, and the decision for the child to have their own room. Children that decides to have their own rooms, after sufficient co-sleeping and gaining confidence, become more independent.
In my opinion, children are not ready for school until they make their first decision of independence -- to end co-sleeping with their parents. Their parents should not force this decision onto them.