Between the two of them, my teenage daughters have been required by their Canadian high school teachers to read—no fewer than three timesone and only one book that purports to introduce them to the African-American experience. Can you guess? It’s Harper Lee’s novel To Kill a Mockingbird. And if they were interested in a contemporary film about the abolitionist movement in Great Britain, all they had to do last year was visit a suburban cinema to watch Amazing Grace, a movie that has the temerity to dramatize the life of abolitionist William Wilberforce while barely showing a black face or