Fourth grade is considered a crucial benchmark for reading, because by that age kids are mostly done with formal reading instruction and have moved on to using their reading skills to master other subjects. But if, like two-thirds of American kids, they are lacking in such skills, they are unlikely ever to catch up. One more bleak detail buried in the data: Though the 66 percent figure is a slight improvement from the 68 percent of kids who weren’t proficient in 2007, the gap between rich and poor fourth-graders continues to widen. Eight years ago, higher-income students were 26 percentage points ahead of lower-income students in reading; now they are 31 points ahead.