Dalton Conley, a sociologist at New York University, doesn't know why low-birth-weight babies are nearly four times as likely not to graduate from high school on time as their siblings. But he and Neil Bennett of the Baruch School of Public Affairs know that it happens, having parsed reams of University of Michigan data on families going back to 1968, and came up with the longest view yet of how underweight babies (5.5 pounds or less) turn out.
Those findings are troubling. The ill effects of low birth weight on social and intellectual development, well documented by previous studies, were previously thought to fade in adolescence; Conley's findings suggest they may be irreparable. In the seemingly controlled environment of families, only 15 percent of the low-weight children graduated high school by 19, whereas 57 percent of their siblings did.
Conley could not answer why — that, he said, will be "for some future researchers to investigate." And there is reason to hope that low-weight children born more recently, with more sophisticated care at their disposal, will fare better than the generation Conley studied. But his findings throw down a heavy gauntlet for those "future researchers" to take up: Discover and combat whatever is causing the cognitive gap that begins in those crucial first months, because it seems to follow a child throughout his life.