Most Christians in the United States know the saying that Sunday morning is the most segregated time in the country on any given week. Though they often think of segregation as segregation by culture, language, skin color or tax bracket, perhaps the most accepted, encouraged and practiced form of segregation is segregation by age. During the 20th century, changes in developmental theory led congregations to sort themselves by age group or "life stage" (children, youth, college, young adult, y...