Which of the following is NOT the characteristic of high-income children?

The behavior gap between rich and poor children, starting at very early ages, is now a well-known piece of social science. Entering kindergarten,(18)high-income children not only know more words and can read better than poorer children but they also have longer attention spans, better-controlled tempers and more sensitivity to other children.
    All of these make the comparisons between boys and girls in the same categories fairly striking: The gap in behavioral skills between young girls and boys is even bigger than the gap between rich and poor.(19)By kindergarten, girls are substantially more attentive, better behaved, more sensitive, more persistent, more flexible and more independent man boys, according to a new paper from Third Way, a Washington research group. The gap grows over the course of elementary school and feeds into academic gaps between the sexes. By the eighth grade, 48 percent of girls receive a mix of As and Bs or better. Only 31 percent of boys do.
    And in an economy that rewards knowledge, the academic struggles of boys turn into economic struggles. Men’s wages are lower than before.(20)Men are much more likely to be idle—neither working, looking for work nor caring for family—than they once were and much more likely to be idle than women.