The first year of school in America, known as kindergarten, usually begins between the ages of five and six. Among rich countries such a late start is something of an anomaly. Barack Obama believes it is an economic and social problem; his education secretary goes as far as to say that it is “morally indefensible”. This statement has some support, as it is clear from research into vocabulary that youngsters from poor families enter kindergarten well behind their peers—a disadvantage that usually lasts a lifetime. Children from households on welfare knew 525 words by the age of three, while the offspring of professionals had mastered 1,116.