Jonathan Kozol has persistently crossed the lines of class and race, first as a teacher, then as an author of books about the children he has called “the outcasts of our nation’s ingenuity.” His new book, “Fire in the Ashes: Twenty-five Years Among the Poorest Children in America,” is about a group of inner-city children he has known for many years, young men and women who have come of age in one of the most destitute communities of the United States, including the South Bronx. He was interviewed about it on WNYC’s The Leonard Lopate Show.