Shortly before Thanksgiving, Arne Duncan made a glib remark about the Common Core that quickly blew up, the Huffington Post reports. Speaking before a gathering of state schools chiefs, the secretary of education dismissed growing opposition to the new national set of learning standards, saying “white suburban moms” were rising up against the Core simply because its more rigorous tests meant they were being told “their child isn’t as brilliant as they thought they were.” The riff wasn’t all that different from Duncan’s usual words of support for the Common Core…