Catholic schools achieved the greatest social transformation in American history, pulling impoverished Irish immigrants out of the underclass and into the working and middle classes, writes Patrick McCloskey, author of The Street Stops Here--an account of a year in the life of a Catholic school in Harlem. These schools now provide a lifeline for disadvantaged, non-Catholic minorities in urban America, boosting graduation and college acceptance rates, and outperforming many equivalent public schools. But they are also disappearing from the very neighborhoods that need them most. McCloskey reports on how one diocese has bucked the trend, what it means to one family, and what it could mean for America. (Contains 14 footnotes.)