When it comes to launching missiles in the Mommy Wars, Sarah Palin has nothing on Christopher Ruhm. On Thursday, the University of North Carolina, Greenboro, economist published a study showing that kids from high-socioeconomic-status families take a long-term hit when their moms work outside the home—at ages 10 and 11, they perform more poorly on cognitive tests and are also more likely to be overweight than those whose high-status mothers leave the workforce. Children from low-status families, on the other hand, don't seem to suffer as much when their moms work. In fact, many of them do better on the same tests, and they're more fit, than similarly disadvantaged kids with stay-at-home moms.
The findings are surprising, and it's easy to read them as a warning to affluent, educated mothers: if you want the best for your child, don't work. (Conversely, if you're not well-off: get your kid to day...