Does rather disadvantage their kids,

actually, many of the amish have a 'rite of passage' that encourages young kids from the ages of 16 to oh, say 24 to experiment with "normal life" to learn to drive, get a job and a car to drive, to buy and listen to radios, tv's, vidio games, ( and as part of this, skate board where introduced to the amish community.. since the 'technology' of skateboard is low, it has been accepted by the community, and all amish kids can skateboard) and to fully experience other aspects of modern US life. Most, but not all, chose to give these things up, and to remain inside the amish comminuty. those that don't are not shunned, but they recognize that visits to their parents and family will be one sided. The children who leave are encourage to come and visit, but most parent will not go and visit their children in cities, or other places where they cannot continue to exercise the amish way of life. when the kids visit, they are expected to honor the amish way of life.

compared to catholoism, where i was "confirmed" as an adult member of the church at the age of 13, long before i was able to independantly think about it, or have any real say--the amish process lets kids try, and experience the non amish life, and hopes (and presumes) kids will chose it freely. Since something like 85% of the kids do, they seem to have some success.

Since the kids who leave never became part of the community as adult, they didn't break any religious law when they left, so they are not shunned.