Recess has, in many school districts, vanished from the schedule entirely. After school, parents shuttle their kids from activity to activity, depriving them of unstructured time alone or with friends. That matters, according to researchers, not just because play reduces stress and makes children more socially competent—which evidence suggests that it does. It matters also because play supposedly improves working memory and self-regulation; in other words, it makes kids sharper and better-behaved. So, ironically, by shortchanging them on play in favor of academics, we may actually be inhibiting their development.