India, Oct. 30 -- At 13, Akbar became the Mughal emperor (though a regent initially governed on his behalf).

At 18, the young Macedonian Alexander was leading soldiers into battle.

Today, children around the world still work in fields, workshops and homes; or as models, entertainers and performers on reality shows.

There has never been a universal experience of childhood.

Many care for siblings or do a substantial share of household work. Pure chance - in the form of class, gender, geography etc - determines how much freedom, protection and choice a child will have.

This essay is chiefly about a narrow group: urban middle-class Indian children, whose families have the means to plan and invest heavily in their future.

For them, child...