Angry that public schools here have always taught American history through a Eurocentric prism, parents of black children began pleading with local school officials to offer a course in African-American history. Paul G. Vallas, head of the school district, said a required black history course was essential. Above, the text that will be used this fall. That was nearly 40 years ago. This year, their pleas were finally - and emphatically - answered. Starting in September, students entering city high schools as ninth graders will be required to take a course in African-American history, making Philadelphia the first major city...