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In the early 1990s, some influential people said that being in single-sex classes could raise a girl’s self-esteem. Schools across the country began creating single-sex classrooms and schools. But many critics claim that all-female schools may actually be detrimental to a girl’ s education because they reinforce the regressive notion of sex differences. The renewed interest in single-sex schooling has fostered a controversy among Americans. Those who give it full endorsement believe girls need an all-female environment to take risks and find their own voices. Those who question the validity of single-sex schooling believe there is no such thing as separate but equal.

Now I’d like to identify some key changes in our cities. First of all, they’re getting bigger and bigger. For the first time in history, there will soon be more people living in urban areas than in rural environments. In 1950, New York City was the only city with a population of ten million. Now in 2010 worldwide we have thirty-eight cities with populations of over ten million people, what we call mega-cities. Cities are also getting taller, because land is getting more and more expensive. We can have a tall apartment building that a thousand people can live in. Skyscrapers have become a symbol of modern cities.