In Huxley's Brave New World, the World State is counting on the idea that there isn't much, if any difference between what a child thinks and what an adult thinks. The leaders of the society have taken every measure to ensure that there is minimal thinking amongst its citizens. If there is any thinking, the World State would fail.
The World State carefully brainwashes and conditions each of its citizens. It designs the citizens so that each "person" will love his or her role in society. Children are conditioned to do this through hypnopaedia, for instance, in which they are told what they love while they are asleep through recordings. This idea is reinforced in adults through the use of soma and sex in the form of "Orgy-Porgies."
The real threat comes into the World State when John comes. He is a thinking man and that is no good for the society. Before they have a chance to send him away, he exiles himself. If the World State had the chance, they would have sent him to Iceland where his thinking couldn't hurt the rest of the citizens.